Scientists have observed many types of tropical fish moving beyond their traditional ocean ranges into waters that have historically been more temperate. These fish compete for food with native fish, consuming much from the kelp forests and beds of sea grass. The expansion of the ranges of tropical fish was most likely caused by — *
A-global droughts that raise the salt concentration of ocean waters
B-the rising temperatures of ocean waters
C-agricultural runoff that contributes to dead zones in the ocean
D-acid rain pollution that lowers the pH of ocean waters