51.

1. alone
2. lonely
3. only
4. isolated

52.

1. indoor.
2. inward
3. relevant
4. flexible

53.

1. back
2. down
3. next
4. near

54.

1. reduce
2. revise
3. descend
4. delay

55.

1. Besides
2. However
3. Anyhow
4. Anyway

56.

1. or
2. and
3. but
4. nor

57.

1. sketched
2. constructed
3. researched
4. developed

58.

1. starts out
2. pulls up
3. looks at
4. makes up

59.

1. because of
2. adhere to
3. instead of
4. regardless of

60.

1. functional
2. beneficial
3. precious
4. sensible

(Reference keys.)