it作形式主语与形式宾语 — 英语填空题
题目
用 it 作形式主语或形式宾语改写句子，在每个空格中填入一个词。① To compare the two study plans carefully is useful. ___ is useful to compare the two study plans carefully. ② The tutor thought that checking every source before writing was necessary. The tutor thought ___ necessary to check every source before writing.