Step 1: Concept
An integral domain is a commutative ring with identity that has no zero divisors.
Step 2: Meaning
"No zero divisors" means if $a \cdot b = 0$, then either $a = 0$ or $b = 0$.
Step 3: Analysis
$(\mathbb{Z}, +, \cdot)$ is commutative and has identity 1. If the product of two integers is zero, at least one of them must be zero. It is not a field because non-zero elements like 2 do not have multiplicative inverses in $\mathbb{Z}$.
Step 4: Conclusion
Therefore, the ring of integers is an integral domain.
Final Answer: (A)