The great hall was crowded with many people, ___ many children ____ on their parents' laps

问题描述:

The great hall was crowded with many people, ___ many children ____ on their parents' laps
a. including; seated b. included; sitting
选A, including在这到底是非谓语动词还是介词呢?
第2个空用sit的话可以吗? 如果用该怎么改?

include是介词,由其领导的这个句子是做状语成分之用.
seated是动词+ed,其引导的"seated on their parents' laps"是后置定语的成分,用来修饰前面的"children".
sit不行,因为这里是个从句.