On a Long Transcontinental Flight, a Middle-Aged Man Gets Up

Multiple Choice

On a long transcontinental flight, a middle-aged man gets up and exercises in the aisle, moving his hands, feet, arms, and legs as much as he can. He does this every two hours. The flight attendant asks him to sit down, but he explains that he is trying to prevent a very dangerous medical condition. He is talking about the condition called

A) leukemia.
B) deep vein thrombosis.
C) aplastic anemia.
D) thrombocytopenia.