51.

1. dilemma
2. dialogue
3. negotiation
4. bargain

52.

1. prosecution
2. execution
3. persecution
4. extinction

53.

1. taken place
2. replaced
3. in place
4. out of place

54.

1. seriously ill
2. severely ill
3. incurably
4. terminally ill

55.

1. very few
2. a few
3. quite a few
4. few

56.

1. subjected to
2. subject to
3. subjective
4. subjecting to

57.

1. value
2. measure
3. measurement
4. rule

58.

1. profound
2. inductive
3. tangible
4. novel

59.

1. be on the alert for
2. watch out for
3. stand for
4. allow for

60.

1. perspire
2. acquire
3. desire
4. require

(Reference keys.)