Answer:
B: 2⁷-1 = 127
Step-by-step explanation:
A Mersenne prime is a prime of the form 2^n -1, where n is also a prime.
Among the answer choices, neither 90=2·3²·5 nor 15=3·5 is prime. Both 2⁷-1 = 127 and 2¹¹-1 = 2047 are of the right form, but 2047 = 23·89 is a composite number.
2⁷-1 = 127 is a Mersenne prime
