If a spacecraft travels 3.6 au per year, in how many years would it travel from earth to mars? a. 0.15 years b. 1.83 years c. 2.54 years d. 3.72 years

Astronomical unit is roughly the distance from Earth to the Sun ( or 149,597,870,700 m ). 
Mars can be between 0.53 au and 2.52 au from Earth, depending on their relative positions. In both cases we will not accept answers B), C) and D).   
If we use the closest range:
0.53 au : 3.6 au/year = 0.1472 ≈ 0.15 years
A)