Scientists have advanced many theories about why human beings cry tears,none of ______ has been proved.( )
whom
which
what
that
It is reported that 40 percent of the land in Brazil________covered with trees.
Either the judge or the lawyers________wrong on the case at that moment.
The poet and ______ pianist is going to give us a talk this afternoon.
The silence in the dark building was scaring. No sound and voice____ heard at that moment.
It is reported that many a new house ____ at present in the disaster area in Gansu Province.