has changed. 因为since 1992 是现在完成时时间状语
has saved. up to now是现在完成时的时间状语
has read. 这是强调影响和结果,所以用现在完成时.（现在完成时的定义）
have dreamed. 现在完成时的时间状语for+一段时间.
这些题都是考察现在完成时的用法.
2. 后面有一个 would难道不是过去完成时吗？能不能写had saved??那个would是定语从句who里面的时态，跟主句无关啊。主句的时态由主句的时间状语决定。the country life he was used to ________(change) greatly since 1992.
up to now ,the program ____________(save)thousands of children who would otherwise have died.
each of the students working hard at their lessions ________________(read)the books.
for many years,people ________(dream)of electric cars.
最好有解释 谢谢
has changed. 因为since 1992 是现在完成时时间状语
has saved. up to now是现在完成时的时间状语
has read. 这是强调影响和结果,所以用现在完成时.（现在完成时的定义）
have dreamed. 现在完成时的时间状语for+一段时间.
这些题都是考察现在完成时的用法.
2. 后面有一个 would难道不是过去完成时吗？能不能写had saved??那个would是定语从句who里面的时态，跟主句无关啊。主句的时态由主句的时间状语决定。