高中英语选择Ten years have passed and many of my former classmates

高中英语选择
Ten years have passed and many of my former classmates aren't_____they were.
Athem Bwhat Cthat Dwhich
I was about to give him a call______he hurried into the room.
Aafter Bwhen Cwhile Duntil
I'm so confused .I cannot figure out _____quite a number of insects and birds are dying out.
Athat Bas Cwhy Dwhen