Answer:
a) The boundary formed when one plate is forced to move down below another one at an ocean trench is called a convergent or destructive plate boundary.
b) The boundary formed when plates move apart at mid-ocean ridges is called a divergent or constructive plate boundary.
c) The boundary formed when plates slide past each other is called a transform or conservative plate boundary.
d) The boundary formed when plates push up against each other and create mountains is called a convergent or collisional plate boundary.