Ⅰ. 用本模块恰当的单词补全语境
1. study biology        学习生物学
2. the staple food                 主食
3. study modern agriculture  研究现代农业
4. selective breeding for better yield 选择性育种以获得更好的产量
5. cross different species of rice     杂交不同品种的水稻
6. make a significant breakthrough    做出重大突破
7. publish the results of his experiment 发表他的实验结果