What is the actual space between a presynaptic membrane and postsynaptic membrane?

Egbert is a quiet child who is very slow to adapt to change. However, if he is introduced gradually to new people or situations, then eventually he will accept them without too much distress. Thomas and Chess would say his temperament is ______

a) active b) slow-to-warm-up c) difficult d) easy

__________is the knowledge that quantity is unrelated to the arrangement and physical appearance of objects

a) Concrete operations b) Conservation c) Centration d) Preoperational operations