51.

1. Either
2. Neither
3. Each
4. Any

52.

1. intended
2. required
3. assumed
4. inferred

53.

1. subtle
2. obvious
3. mysterious
4. doubtful

54.

1. maintained
2. described
3. settled
4. afforded

55.

1. in the light
2. by virtue
3. with the exception
4. for the purpose

56.

1. reduction
2. destruction
3. deprivation
4. restriction

57.

1. upon
2. by
3. through
4. with

58.

1. paid attention to
2. caught sight of
3. laid emphasis on
4. cast light on

59.

1. develop
2. produce
3. stimulate
4. induce

60.

1. if
2. as if
3. only if
4. if only

(Reference keys.)