what moon phase would you find when the earth, sun, and moon make a 90-degree angle
to each other?

First quarter or the quarter moon in the phase when the earth, sun and moon make a 90- degree angle.

Explanation:

In this phase the moon arises in the noon and sets in the midnight. They can be seen in the after noon or even in the early evening high in the sky. The shape of the moon is half or can say the lighted half. In simple language the moon seen in the day time is the first quarter moon. Here, in this phenomenon the sun and the moon makes the 90- degree angle earth.

c) up is the direction the magnetic force is acting on the charge.