Question

there a lot of visitor in his house,he has no time to talk with you

.there a lot of visitor in his house,he has no time to talk with you.
A.are B.being 为什么不选A?

Answer 1

一个句子只能有一个谓语（可以是系动词也可以是实义动词），题目是一个句子，而后面部分he has no time to talk with you是主干，there being a lot of visitors in his house可以理解为后面部分的原因，是一个状语，不能独立成为一个句子,如果要成为句子必须要用相关的连接词连接比如so（所以）。相关例子还有：
Walking in such an empty street,he feels very afraid.
With a lot of homework to do,he decided not to watch TV.
其中前一句是动名词做状语表示伴随，后一句是介词短语作状语表示原因。

Answer 2

前后两个半句之间用逗号连接，说明这是一个句子，一个句子只能有一个动词，如果选A，这个句子就有了两个动词：has,are，而B是一个非谓语，不是动词