Achievements of the Gupta Empire A. Developed advanced medical treatments
B. Formed an alliance with Alexander the Great
C. Built the first Hindu temples
D. Captured all Mauryan territory

i believe the answer is, C.

Explanation:

The Gupta Dynasty, were the first to build the Hindu temples which evolved from the earlier tradition of rock-cut shrines. Adorned with towers and elaborate carvings, these temples were often dedicated to all the Hindu gods.

(202 bc - 220 ad) dynasty started by lui bang; a great and long-lasting rule, it discarded the harsh policies of the qin dynasty and adopted confucian principles; han rulers chose officials who passed the civil service exams rather than birth; it was a time of prosperity