Girls usually like _______ with friends while boys like playing basketball or soccer on weekends.
A:working out
B:hanging out
C:helping out
D:taking out
根据句意, 用括号内所给单词的适当形式填空。
母爱是伟大的,母亲在怀孕期间,身体负担明显加重,她要为胎儿提供所需的养料和氧气,排出胎儿产生的二氧化碳和其他废物,母亲与胎儿之间进行的物质和气体交换发生在( )