题目选项分析

The observations garnered from two independent research studies corroborate the theory that crows have a tremendous intellectual capacity; the studies show crows as capable of understanding basic causal relationships—a capacity that puts them on the same level as a human seven-year-old—and to create independently their own tools.

The observations garnered from two independent research studies corroborate the theory that crows have a tremendous intellectual capacity; the studies show that crows are capable of understanding basic causal relationships—a capacity that puts them on the same level as a human seven-year-old—and independently creating their own tools.