Q7

Consider the proposition: “If $2^n-1$ is not prime, then $n$ is not prime”. Given that each of the following statements is true, which statement disproves the proposition?

A. $2^5-1$ is prime
B. $2^6-1$ is divisible by $9$
C. $2^7-1$ is prime
D. $2^{11}-1$ is divisible by $23$