Using the divisibility tests, a number is divisible by 10 exactly when its last digit is which of these?

1. The divisibility test for 10 checks only the final digit of the number. 2. A number is divisible by 10 if it ends with 0. 3. Ending in 5 makes a number divisible by 5 but not by 10, and an even last digit only guarantees divisibility by 2. _Source: OpenStax Elementary Algebra (CC BY 4.0), Ch 1 "Foundations", section 1.1 Introduction to Whole Numbers_