Scientists have advanced many theories about why human beings cry tears,none of ______ has been proved.( )
whom
which
what
that
He can’t tolerate by her again and again during the report, so they quarreled at last.
______ the instructions very carefully when filling in the form.
The school had promised to keep parents fully _____ about the conditions of their children at school.
I send you my revised catalogue and price list, ______ you may find something that suits you.
When he came back, he found his bag over the seat.