Comprehension:
In the following passage some words have been deleted. Fill in the blanks with the help of the alternatives given. Select the most appropriate option for each number.

In a long duration space flight, besides the obvious 1.______ of meteors, rocky debris, and radiation, 2.______ will have to deal with muscle atrophy 3.______ by weightlessness; therefore, when they return to Earth, they face a 4._______ period of weight training to rebuild their strength after the 5._______ space flight.
SubQuestion No : 72
Select the most appropriate option to fill in blank No.2.