What is the weight of an object(mass = 60 kilograms) on mars, where the acceleration due to gravity is 3.75 meters/seconds?

The weight of ANY object located ANYwhere is the product of

(the object's mass) times (the gravity at that place).

If the acceleration of gravity happens to be 3.75 m/s², then

Weight = (mass) x (3.75 m/s²)

Weight = (60 kg) x (3.75 m/s²)

Weight = 225 Newtons . (about 50.6 pounds)

The same 60-kg object would weigh 588 N (about 132 pounds)
on Earth, and 97 N (about 22 pounds) on the moon. 

The answer is C, nitrogen.
In normal air in the atmosphere, about 78% is nitrogen, following by oxygen, 21%
Note that when we breathe in air, the oxygen we breathed in is used in body, not nitrogen. The amount of nitrogen in unbreathed air and breathed air is about the same. Instead, we exchange oxygen with waste product, which happens to be carbon dioxide. So what we breathes our is mainly nitrogen, carbon dioxide, very little amount of oxygen and other noble gases.