在管式空气预热器中,烟气和空气两种介质不会交替流过受热面。
A. 正确
B. 错误
遗精是一种生理现象,是男孩迈入青春发育期后的一种自然生理现象,也是男性生殖腺开始成熟的标志,不必产生心理上的紧张或羞涩感。
A. 正确
B. 错误
He had his book () at his own expense.
A. print
B. printed
C. to print
D. printing
The weather was good except for an () shower.
A. optional
B. intentional
C. additional
D. occasional