TOEFL Listening: TPO-TOEFL阅读TPO - 19L75JA84Z49H18HN$

Which of the sentences below best expresses the essential information jn the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. We now have ample proof that ants benefit plants. B. Barbara Bentley has called for additional proof that ants benefit plants. C. In 1977 Barbara Bentley conducted research that proved that all prior studies were wrong. D. Proof that ants benefit plants will require many more observations and experiments.