《城镇燃气设计规范》中规定液化天然气管道宜采用（）的方式进行补偿。（条款9.4.5）
A、自然补偿
B、强制补偿
C、人为补偿
D、补偿器
参考答案：B
—Don't forget to post the letter, will you?
— I __________ it. [ ]
A. would post
B. had already posted
C. have already posted
D. was posting
慢性支气管灸并发肺气肿时，最早出现的病理生理改变是
A．时间肺活量降低B．生理无效腔气量增大C．通气血流比例失调D．残气占肺总量百分比增加E．低氧血症
