1. Ever since they were first put on the market in the early 1990s, genetically modified (GM 转基因) foods have been increasingly developed and marketed in many countries in the world, mainly on the basis of their promise to end the worldwide food crisis.
【句式翻译】
【句式分析】
【词语点拨】basis n. 基础；构成短语：on the basis of 以……为基础
不要以相貌取人。
史密斯先生定期去健身房。
【语法点拨】现在完成时的被动语态，具体用法参见第11句。
