Conservation refers to a child's ability to recognize that the volume or amount of a substance or object does not change when its form or shape changes. This ability develops in the concrete operational stage around the age of 7 to 11 years old. Before the development of conservation, if a fat, wide glass of water is poured into a thin, tall glass, then the child might believe that the amount of water has decreased since the second glass appears slimmer. All the other choices are actual developmental stages in Piaget's sequence, but the stage in which conservation first develops is in fact the concrete operational stage.

Piaget says every human goes through a variety of stages in our cognitive development in a fixed way. The correct order is sensorimotor (0-18 months), preoperational (2-6 years), concrete operational (6-12 years), and formal operational (12-adult). 

Crystallized intelligence is acquired through experience and refers to general knowledge that is stored in long-term memory. Fluid intelligence refers to a person's ability to reason and problem solve when encountering new situations. Fluid intelligence is innate; therefore, it is not based on learning and experience. For most people crystallized intelligence increases into adulthood and fluid intelligence begins decreasing after adolescence. 

Jean Piaget described how children adapt to the world through assimilation or accommodation. "Assimilation" occurs when a child encounters a new object and uses an already existing schema to identify it. In this example, the child is exposed to a cat and uses the existing schema of "doggy." On the other hand, "accommodation" occurs when a child encounters a new object and changes an existing schema. "Conservation" is a term that Piaget uses to describe a child's ability to understand volume (i.e. a quantity remains the same despite a change in appearance). Conservation develops during the concrete operational stage. "Egocentrism" is characteristic of the preoperational stage and refers to a child's inability to see other people's point of views. Last, 'object permanence" is characteristic of the sensorimotor stage and refers to a child's ability to understand that objects continue to exist even when they are hidden. 

Erik Erikson developed the idea behind identity vs. role confusion, which comes from his theory of psychosocial development.

Erikson's theory proposed eight stages: trust vs. mistrust, autonomy vs. shame, initiative vs. guilt, competence vs. inferiority, identity vs. role confusion, intimacy vs. isolation, generativity vs. stagnation, and integrity vs. despair.

Generativity vs. despair is not one of the stages of psychosocial development. Generativity vs. stagnation and integrity vs. despair are two stages of Erikson's theory. 

The stage known as "intimacy vs. isolation" takes place during the period of young adulthood, roughly encompassing ages 18-35. The young woman in the question falls firmly within this range.

Erikson would say that this boy is at the developmental stage during which he is grappling with his own autonomy. This stage is known as "autonomy vs. shame and doubt," and typically takes place during ages 1-3 years.

Relational aggression typically involves more covert behavior, such as spreading rumors or gossiping about others in an attempt to manipulate one's friendships and faciltation exclusion. This type of aggression is represented in the given question.

Physical aggression involves physical harm to another person, such as hitting, punching, kicking, or even vandalizing or damaging one's property. 

There is no such thing as nonverbal aggression. 

Reactive aggression is typically an angry, defensive response to provocation, particularly when one is blocked from reaching a goal or is harmed first. 

Marcia's theory pertaining to identity development and statuses involves two dimensions: exploration and committment. 

Individuals who are actively exploring their options before making a final decision, such as the young man described in this question, are classified in the moratorium identity status. 

Individuals who have made a decision after active exploration as classified in the achievement identity status. 

Individuals who make a decision without doing any exploration are classified in the foreclosure identity status. 

Individuals who do not know what they want to do and who are indifferent to exploring are classiged in the diffusion identity status.