subjects were asked to learn some words using imagery,using

不可以 were asked to 这里已经是谓语动词 所以后面的use要变为非谓语形式 加ing
如果你想换成used 就要在前面加个and 变为subjects were asked to learn some words and used imagery
然后是没有to used 这种改法的
再问： 我说的是改成to use imagery，可以吗，谢谢
再答： 不可以