From the half-life for 14c decay, 5715 yr, calculate the age of the shroud.

Are you referring to this question?
"The cloth shroud from around a mummy is found to have a 14C activity of 9.7 disintegrations per minute per gram of carbon as compared with living organisms that undergo 16.3 disintegrations per minute per gram of carbon. From the half-life for 14C decay, 5715 yr, calculate the age of the shroud. (Radioactive decay follows the first-order kinetics.) "

Solution:
[A]₀ = 16.3 dpm/g                    
[A]∨t = 9.7 dpm/g
t ∨1/2 = 5715 yr.
t=?

[A]₀ / [A]∨t = 16.3/9.7 = 2 ∧t/t ∨1/2
t/t∨1/2 = log 1.168/ log 2 = 0.225 / 0.301
           = 0.747
5715 years × 0.747 = 4270 years

Ithink your answer is d

No it doesnt because it can be any number.