The book ______ I borrowed from the library is very interesting.
that
which
who
whom
This is the man ______ helped me yesterday.
whom
who
which
whose
The girl ______ you met at the party is my sister.
who
which
whose
whom
The house ______ roof is red belongs to Mr. Smith.
whom
which
who
whose
The reason ______ he was late is still unknown.
whom
who
why
which