Mercury Is Very Hard to Observe from Earth Because

Multiple Choice

Mercury is very hard to observe from Earth because:

A) it always appears as only half lit from Earth.
B) it never gets more than 28 degrees from the Sun's glare.
C) its elliptical orbit causes it to change speed unpredictably.
D) its barren surface reflects too little sunlight; it is almost invisible always.
E) its very rugged surface does not allow radar to bounce back to Earth.