51.

1. complex
2. vital
3. restricted
4. remarkable

52.

1. varying
2. difficult
3. hazardous
4. distressful

53.

1. mental
2. visual
3. graphic
4. demographic

54.

1. putting
2. getting
3. reinforcing
4. piecing

55.

1. few
2. little
3. much
4. inadequate

56.

1. testify
2. affirm
3. identify
4. certify

57.

1. flexible
2. independent
3. frequent
4. skillful

58.

1. expanding
2. extending
3. continual
4. desperate

59.

1. behaviors
2. concepts
3. awareness
4. memory

60.

1. comfortable
2. effective
3. efficient
4. efficacious

(Reference keys.)