If the stars at the turnoff point in a star cluster have masses of about four solar masses, how old is the cluster

age of the cluster is 3.125 × 10⁸ years

Explanation:

Given that;

stars at the turnoff point in a star cluster have masses of about 4 solar masses

Age of the cluster?

we know that the main sequence lifetime of a star in solar lifetime(t) is related to the mass of the star in solar masses(M). expressed as

ζ = M^(-5/2)

our M is 4, so we substitute

ζ = 4^(-5/2)

ζ =  0.03125 solar lifetime

now convert the lifetime of star cluster into years

ζ = 0.03125 solar lifetime × (10¹⁰ years / 1 solar lifetime)

ζ = 312,500,000 ≈3.124 × 10⁸ years

therefore age of the cluster is 3.125 × 10⁸ years

it is very well related to a lot of things but with my limited knowledge i can confidently say that the answer is space.

your answer is c! hope this : )