After alexander the great, but before the rise of the gupta empire, which other empire politically and economically united most of present-day india, pakistan, and afghanistan? a) harappa b) maurya c) nanda d) qin

B) Maurya Empire

Explanation:

After the death of Alexander the Great in 323 BC, most of present-day India, Pakistan, and Afghanistan were united by the Maurya Empire, which existed from 322 BC to 185 BC. This empire was the largest political entity to have existed on the territory of the Indian subcontinent (you can see the map below).

Both Harappa (3300 to 1300 BC) and Nanda (5th or mid-4th century BC to 322 BC)  existed earlier and didn't include all of the listed territories. Qin dynasty was the first Imperial dynasty of China, so answer D is also incorrect.