Hello!
She makes the conjecture that all odd numbers are prime numbers.
It is false, we have infinite counterexamples, let's analyze the alternatives and mark some:
• The number 21 is an odd number and not prime.
True, because 21 can be divided by: 1, 3, 7, 21.
• The number 9 is an odd number and not prime.
True, it can be divided by 1, 3, 9.
• The number 15 is an odd number and not prime.
True, it can be divided by: 1, 3, 5, 15.
• The number 23 is an odd number and is prime.
True, it's prime. BUT it isn't a counterexample, just an example as mentioned in the exercise.
Answer:
You'll select the alternatives: 1, 2 and 3.
