题目内容：
According to the passage, which of the following is true?
A．Roger Fours taught sign language to three younger chimpanzees. B．Washoe was the first chimp to use American Sign Language.
C．A chimpanzee died of natural causes in Africa at a research center.
D．Nowadays there are still lots of scientists experimenting with chimpanzees.
参考答案：
答案解析：