Water because hydro means water
The correct answer is b.
The child is reaching for a toy which is not visible to him (hidden under a cloth), therefore, the child has a mental representation of the object in his/her mind. This action means that the child acknowledges that the objects continue to exist even when he/she can not hear or see them. This thought process is called object permanence and it is an ability acquired between the 4th and 7th month of a child's development.
To avoid any injuries or emergencies <span />
