Which vitamin plays a primary role in vision and the development of body cells?
a. vitamin a
b. vitamin b6
c. vitamin c
d. vitamin d

during longer space exploration trips, crewmembers may develop vision impairment risks and short-term cardiac atrophy or a decrease in the size, strength, weight, and activity of the heart during space flight because they can experience microgravity. in addition, the long-term medical condition is loss of bone mineral density and radiation exposure.