The boundary between the illuminated and unilluminated hemispheres of the moon is known as the
a. terminator.
b. dark line.
c. grey line.
d. border.

The terminator is the dividing line between the illuminated and the unilluminated part of the moon.

Magma forms by partial melting of upper mantle and crust. partial melt means that only a fraction of the available material forms a melt, and that the remainder stays solid. the partial melt rises because of its lower density and ascends through he crust. this is so conclusive mean the answer would be magma igneous rocks or balistic magma.