51.

1. popular
2. known
3. catch on
4. turn out

52.

1. even
2. only
3. simply
4. rather

53.

1. faster
2. fastest
3. the faster
4. the fastest

54.

1. of
2. from
3. off
4. out

55.

1. has been filled
2. has to be filled
3. is filled
4. will be filled

56.

1. that
2. what
3. which
4. how

57.

1. meaning
2. culture
3. popularity
4. number

58.

1. expected
2. expectant
3. exceptive
4. exclusive

59.

1. those
2. others
3. ones
4. some

60.

1. when
2. where
3. which
4. that

(Reference keys.)