51.  A light machine gun opened up, then another.

52.  A literature search has to be made by the learner, who then makes an assessment of the particular problem.

53.  A long pause, then the pointer went to fifty.

54.  A manual of advice on how best to forecast the demand for new rail services of various types will then be prepared.

55.  A mile out of town his father stopped the mules and then got out his knife to cut each boy a sample.

56.  A minimum level is set and those at or above that level are then selected by non-academic criteria.

57.  A moment passed, and then Derby burst into tears.

58.  A muted grumbling followed, then the slamming of a door.

59.  A new machine or household product existed first as idea, then perhaps as rude sketch.