71.   Although the cause of osteoporosis is unknown, the rapid drop in estrogen production that occurs during menopause is a definite risk factor.

72.   Although the shootings occurred during deer-hunting season, Reeves said he doubted they were accidental.

73.   Although the trial has been the scene of repeated shouting matches between lawyers, most have occurred during hearings when jurors were not present.

74.   An example of why attending is a good idea occurred during a British Isles cruise on a Princess ship.

75.   An actual surplus could not have occurred during a period when the national debt rose.

76.   And a large number of those sales occur during the holiday season.

77.   And damage from other earthquakes that had occurred during the years was highly visible.

78.   And it explains why sleepwalking almost always occurs during nondream sleep, when the muscles are not paralyzed.

79.   And in the third, the events can occur during the period known as REM sleep, when the eyes are moving rapidly and dreams are most likely.

80.   And they say exploration of the coastal plain could occur during the winter, when animals are not present and no habitat would be disturbed.