So sudden______that the enemy had no time to escapeA.did the attack B,was the attack这里的答案是A,那么did 和was的区别在哪儿

So sudden______that the enemy had no time to escapeA.did the attack B,was the attack这里的答案是A,那么did 和was的区别在哪儿 So sudden______that the enemy had no time to eacape.a did the attack b the attack didc was the attack d the attack was 一道英语选择题,求详解So sudden______that the enemy had no time to eacape.A.did the attackC.was the attack但我不明白为什么选C,选A不可以吗? so so so so so so so, So SO so so So... so So so