1. most land vertebrates can't drink seawater because
a. less water would need to be excreted by the kidneys. b. their kidneys can't excrete concentrated salt. c. their cells would eventually swell. d. they don't have kidneys.

The correct answer is B. their kidneys can't excrete concentrated salt. Since salt is dissolved in water, the organism sends its water reserves to the kidneys to dissolve and excrete the salt but this leads to dehydration. That's why people at sea who don't know what they're doing often dehydrate themselves by drinking sea water, thinking that they're safe.