There are exactly 25 prime numbers between 1 and 100, starting from 2 and ending with 97. You can systematically count them or use the Sieve of Eratosthenes to identify all primes in this range.
There are exactly 25 prime numbers between 1 and 100 (2, 3, 5, 7, 11, ... up to 97), a count well established in basic number theory. The other options are common miscounts that result from including or excluding numbers incorrectly.