Final answer:
To determine the total mass of the boy and the bicycle, we add the mass of each together, which is 45 kg for the boy plus 15 kg for the bicycle. The total mass is thus 60 kg.
Step-by-step explanation:
The total mass of the boy and the bicycle can be found by adding the mass of the boy and the mass of the bicycle. The boy has a mass of 45 kilograms, and the bicycle has a mass of 15 kilograms. To find the total mass, we simply add these two masses together.
45 kg (boy) + 15 kg (bicycle) = 60 kg (total mass)
Therefore, the answer is 60 kg, which is option A.