51.

1. digress
2. progresses
3. recedes
4. divert

52.

1. psychiatrist
2. hypnotist
3. therapist
4. pharmacist

53.

1. effect
2. infect
3. affect
4. defect

54.

1. evolves
2. involves
3. revolves
4. develops

55.

1. mistaking
2. mistakenly
3. mistaken for
4. mistaken

56.

1. manifestations
2. forestations
3. simplifications
4. manufactures

57.

1. doubted
2. suspected
3. distrusted
4. mistaken

58.

1. necessary
2. present
3. available
4. any

59.

1. retrieve
2. retreat
3. contract
4. withdraw

60.

1. deserted
2. abandoned
3. exterminated
4. lost

(Reference keys.)