The body has both physical and chemical ________ to prevent invaders from entering

Current recommendations suggest that you try to get at least 30 minutes of exercise, _____ to _____ days a week

Fill in the blank(s) with correct word

A ____ rescue is rescue over a chasm or ravine where the rescuer or patient is suspended in mid-air with only the rope for protection from a fall.

A. low B. steep C. high D. highline