If a number is divisible by 10, then it is divisible by 5.

Which of the following arguments is valid with respect to the conditional statement premise above?

1. A number is divisible by 10.
Therefore, it is divisible by 5.
2. A number is divisible by 5.
Therefore, it is divisible by 10.
3. A number is not divisible by 10.
Therefore, it is not divisible by 5.
4. A number is not divisible by 5.
Therefore, it is not divisible by 10.

A. 1 only
B. 2 and 3
C. All arguments are valid.
D. 1 and 4