按照作用范围的不同，通风系统可以分为通风和通风系统两大类。
查看答案
I have a lot of books, half of ________ novels.
A. that
B. which
C. them
D. whom
The girl in the snapshot was smiling sweetly, her long hair _________.
A. flowed in the breeze
B. was flowing in the breeze
C. flowing in the breeze
D. were flowing in the breeze
On Sundays there were a lot of children playing in the park, _________ parents seated together joking.
A. whose
B. which
C. their
D. that
微信支付 
支付宝支付