Select the most appropriate option to substitute the underlined segment in the given sentence. If there is no need to substitute it. select No improvement.

The avalanche of new data have been as overwhelming that many scientists who were skeptical about Bronze Age migrations into India have changed their opinions.

A

The avalanche of new data has been as overwhelming

B

The avalanche of new data has been so overwhelming

C

The avalanche of new data have been so overwhelming

D

No improvement