In dry weather ,the flowers will have to be watered if they__A. have survived b. are to survive c. would survive d. will survive为什么要用不定式呢 有点不明白 不定时也是表将来的一种呀 状语从句一般都用一般现在表将来 ,这题为何不用 survive 原形呢 ?为什么没有 survive 这项呢

In dry weather ,the flowers will have to be watered if they__
A. have survived b. are to survive c. would survive d. will survive
为什么要用不定式呢 有点不明白 不定时也是表将来的一种呀 状语从句一般都用一般现在表将来 ,这题为何不用 survive 原形呢 ?
为什么没有 survive 这项呢