来自刘渭洁的问题
itisdifficulttodo/doingitisdifficult后接todo还是doing
itisdifficulttodo/doing
itisdifficult后接todo还是doing


itisdifficulttodo/doingitisdifficult后接todo还是doing
itisdifficulttodo/doing
itisdifficult后接todo还是doing
itisdifficult/adj.todosth.