He would have given you more help, if he ________ so busy.
A、havenotbeenB
本題考察與過去事實相反的虛擬語氣。
Itrainedhardyesterday,______preventedmefromgoingtothepark.
Ittookmeamonthtogetrid_______thecough.
Thenewdiscovery_______beofgreatservicetomankind.
Decisiononwhetherthemessageisrightorwrongshouldatleastcomeafter_____whatthemessageis.
Wateriscomposed_______hydrogenandoxygen.
