When a child understands that things and events continue to exist even though one can't see or hear them, we say that the child understands
a. intuitive thought.
b. mathematical theory.
c. object permanence.
d. conservation.

The correct answer is : c. object permanence

Object permanence is a sign of development of infant's social and mental capacities.

Example of object permanence : when infant is already aware that he/she has a dad. Even though the dad went to work and the infants can not see them , the infants still acknowledge his existance 

It should be at the center of any map going vertically: the prime meridian, as it passes through greenwich,  england, is considered 0 degrees longitude

This is highly correct because infact i just had a essay done yesterday so yeah that's pretty much what you need to do