【单选题】
The policemen（ ） many cases by following the footprints left at the scene of crime.
①
investigate
②
investigated
③
has investigated
④
have investigated
【单选题】
There are many children（）behaviour is generally unacceptable.
①
who
②
whom
③
whose
④
that
【单选题】
—How many people are there in Changsha?—About six ______.
①
million
②
millions
③
millions of
【多选题】
Do you know that there are many ______ animals in the zoo?
①
A.kinds of
②
B.types of
③
C.sizes of
④
D.A.sorts of