Answer: B: Orbital radius would decrease because the gravitational pull would increase.
The gravitational force depends on the mass of the two bodies and the square of the distance between them. If the sun is replaced by Betelgeuse which is twenty times heavier, it would exert 20 times greater force on the Earth. Hence, it would pull the Earth closer. This would change its present orbit. The orbit would decrease.
Therefore, the right option is B: Orbital radius would decrease because the gravitational pull would increase.
