Leticia is a space scientist who made this diagram of the Moon and Earth as seen from above (top view), with sunlight coming from the left, as shown by the arrows. Why does Leticia’s diagram show that it’s brighter on the left half of the Moon?

A). Because Leticia’s diagram is showing that the half of the Moon that is facing the sun is lit by the sun, and the other half is dark.

Explanation:

Leticia's diagram display that the left half of the moon was brighter as her diagram shows that 'half of the moon facing the sun was ignited/lit by the sun while the half part which remained unlit was dark.' This is the key cause of day in the one part of the Earth(lit by the Sun due to the Earth's tilted axis) and night in the other part. Thus, option A is the correct answer.