Why did the Mongols repeatedly fail to conquer the Sung dynasty before Kublai Khan’s conquest?

A. The Sung army had trebuchets.
B. The Sung army had a blockade.
C. The Sung army had battering rams.
D. The Sung army had greater numbers.

However, the Song dynasty was difficult to conquer because of the strategic location of Xiangyang, which became a vital position for Kublai to capture and hold. The city guarded the waterways of South China because the Han River was a major tributary into the Yangtze River.

the answer to 4 is D

the answer to 5 is C