The statement below is followed by four options. Each option is related to the item in the statement, but only one is always true. Select the option that always holds and makes the statement true.
"A prime number always has ______."
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Exactly two factors
The answer must hold for every prime number, without exception. An option that is present in most cases but can be missing in even one case is not always true.
Option (1) An odd value — 2 is a prime number and it is even.
Option (2) A last digit of 1, 3, 7 or 9 — 2 and 5 are prime numbers that end in 2 and 5.
Option (3) Two or more digits — 2, 3, 5 and 7 are prime numbers with one digit.
Option (4) Exactly two factors — a prime number is a number greater than 1 whose only factors are 1 and the number itself, so it always has exactly two factors.