icouldn't ()what they were saying, for they spoke to me at once

选B
C是听见的意思
事实上根据后面的原因，他是听到了，
但是因为他们只说了一次，所以我没有记住他们讲的话。

C听见

correct answer is C. (hear).
qita bu neng peihe.

B
意思是1. 辨别出 I could hardly make out anything in the thick fog. 在浓雾中我几乎什么也看不见。2. 填写;写出 The teacher has made out a list of reference books. 教师已开出了一份参考书单。3. 理解 We can't make out what he is saying. 我们不懂他在说什么。

B
B make out make out 有明白理解的意思
A 是在听，与couldn't 不符
C hear 是听到听得见的意思，与下文what they were saying 不符
D make up 是组成 构成的意思，是干扰项