Question

So many people___,the meeting had to be put off.选B

A were absent B being absent Cbeen absent D had been absent 为什么不能选A 这是一个什么成分

Answer 1

B
本题考查非谓语动词。
不能选A的原因是从句没引导词，如改成：Because/As so many people were absent, the meeting had to be put off.就可以了。
So many people being absent为独立主格结构，非谓语动词作状语时要求其逻辑主语和主句主语保持一致，本题由于不一致，故用独立主格结构。

Answer 2

选A的话，句子就变成了一个run-on sentence（中文好像叫流水句吧，即两个独立的句子，中间却没有适当的连词连接），从语法上来说是一个病句，但口语无所谓的。

Answer 3

句意理解
因为很多人缺席会议取消了。
只有现在分词可以表达原因，作原因状语，是它伴随用法的延伸。