Piaget identified four stages of cognitive development: sensorimotor, pre-operational, concrete operational, and formal operational. Each stage is correlated with a series of essential developmental milestones, such as language acquisition and ability to perform simple mathematical calculations. The sensorimotor stage extends from birth to approximately age two, when the child first begins to speak. The pre-operational stage extends from age two to age seven, encompassing the development of imaginative rather than logical or concrete capabilities. The concrete operational stage takes place between ages seven and eleven, during which the child develops logical processing. The formal operational stage extends from age eleven to late teens (15-20) and is defined by the development of higher level thought, such as deductive reasoning, hypothetical thinking, and problem-solving skills.

For this question, we are looking for an answer choice between ages seven and eleven.

Each stage reflects a dialectical struggle between two tendencies, resolution of each conflict results in healthy personality and the acquisition of basic virtues.

The first stage occurs during infancy, and its basic conflict is Trust vs. Mistrust. At this stage, the child develops a sense of trust when caregivers provide consistent and reliable care and affection. This is akin to the formation of secure attachment as described by attachment theory.

The second stage in Erikson’s model occurs during early childhood. During this stage, the child must resolve the conflict of Autonomy vs. Shame and Doubt. Children discover their independence using different skills and abilities (e.g. potty training, learning to tie their own shoes, etc.). Success leads to feelings of autonomy, while failure results in feelings of shame and doubt.

The third stage occurs during the preschool years; the conflict to be resolved is Initiative vs. Guilt. Children try to assert control over their environment and begin to feel a sense of purpose when they succeed. If the child experiences disapproval as a result of their attempts, a sense of guilt is instilled.

The fourth stage in Erikson’s model deals with the conflict of Industry vs. Inferiority. Children are in the midst of coping with new academic and social demands. Success leads to a sense of competence, while failure results in feelings of inferiority.

The use of abstract reasoning and logic emerges during the formal operational stage. Adolescents who reach this fourth stage of intellectual development are able to logically use symbols related to abstract concepts, such as algebra and science.

While intriguing, the other choices are incorrect. The key feature of the preoperational stage is egocentrism. During this stage, children are able to think about things symbolically. Their language becomes more mature and they develop memory and imagination; however, their thinking is based on intuition and still not completely logical (i.e. they cannot yet grasp more complex concepts such as cause and effect or comparisons). At the concrete operational stage, children’s thinking becomes less egocentric and they are increasingly aware of external events. Children develop operational thinking, but still can’t tackle a problem with several variables in a systematic way. The sensorimotor stage occurs during the first two years of life. Infants are constantly experimenting with objects, using their senses to familiarize themselves with the world, such as by putting things in their mouths, and learning about the world through trial and error. Last, the assimilation-accommodation stage is not one of Piaget's developmental stages.

Morality is a set of standards of conduct that is specific to the social group one is embedded in. Socialization is the process by which one person becomes a member of a group, and learning the moral standards of the group is important to retaining group membership. This means that morality cannot develop in isolation, since it is a group-level concept. Morality also does not develop through genetics; although genetics may play a role in a person’s ability to behave morally, the particular moral standards a person holds are learned from the social group they are embedded in. Last, compliance is defined as going along with what others in a group think is right, but it does not imply that the person who is compliant actually agrees with the actions of the group.

The concept being addressed in this question is the principle of conservation, in which children learn that quantity stays the same even with changes in shape. The best example is when pouring the same amount of liquid into containers of varying shapes. Children learn this principle in Piaget's concrete operational stage (ages 7 to 11). 

The other listed stages in Piaget’s model are incorrect. The sensorimotor stage is from infancy to age 2, during which they learn the principle of object permanence—objects continue to exist even when they cannot be seen. The preoperational stage is from ages 2 to 7. It is when children learn that symbols and language can be used to represent things; however, they still cannot use logical reasoning. The final stage is the formal operational stage, from age 12 through adulthood. Abstract and moral reasoning develop during this stage. 

If the correlation coefficient is 0.3, then the proportion of variance explained by the independent variable is 9 percent.

In other words, the correlation coefficient is denoted as follows:

The explained variance is found using the following formula:

Thus, 81% of the variance remains unexplained by variations in the independent variable.

While all lobes of the brain directly influence each other and intercommunicate, the "frontal lobe" is the area of the brain most directly involved in executive functions such as self-control, planning, reasoning, and abstract thought.