if
［误］ If it will rain I won't go to school tomorrow.
［正］ If it rains I won't go to school tomor row.
［析］ 由if引起的状语从句要用一般时表示将来。
［误］ I want to know if he comes here tomorrow.
［正］ I want to know if he will come here tomorrow.
［析］ if所引起的如果是宾语从句则不能用一般现在时表示将来。
［误］ I wan t to know if it will rain tomorrow he will come or not.
［正］ I want to know if it rains tomorrow he will come or not.
［析］ 这里的if从句是整个宾语从句的条件状语，所以，还应用一般时表示将来。
