摘要
Questions 21 to 25 are based on the following passage: Animals seem to have the sense to eat when they are hungry and theydo not eat more than their bodies need. It has been demonstrated that ratswill, when given a choice over a period of time, prefer water with vitaminsto water without vitamins, even though there is no difference in taste
出处
《当代外语研究》
1994年第2期22-32,共11页
Contemporary Foreign Language Studies
