_____ is all that I can spare. Which is wrong? [ ]

Susanwas reading a newspaper on the train_________ a strange old man come over.

That tests can actually give measurement of thelanguage skills of the students_______ by many teachers.

I was told that by 1990 things werebeginning to improve, _________ quickly enough.

Taobao.com is one of ________shopping websites in China.