The expansion of the ranges of tropical fish was most likely caused by- A. agricultural runoff that contributes to dead zones in the ocean

B. global droughts that raise the salt concentration of ocean waters

C. the rising temperatures of ocean waters

D. acid rain pollution that lowers the pH of ocean water

C

Explanation:

The expansion of the ranges of these fish was most likely caused by the rising temperatures of ocean waters. This is because these types of fishes live in both fresh-water and salt-water but only in aquatic tropical environments around the world. The increase in temperatures of ocean waters has provided more suitable habitats for these fishes to expand to.

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.