51.

1. discovered
2. circulated
3. launched
4. transmitted

52.

1. narrowing
2. widening
3. getting
4. bridging

53.

1. shake
2. pass
3. rocket
4. impress

54.

1. force
2. fight
3. false
4. fault

55.

1. As
2. When
3. While
4. Since

56.

1. lies in
2. shows off
3. results in
4. departs from

57.

1. cultural
2. literate
3. native
4. responsible

58.

1. foster
2. hamper
3. reform
4. advocate

59.

1. statistics
2. average
3. tendency
4. category

60.

1. increase
2. challenge
3. pressure
4. complaint

(Reference keys.)