Find the missing number?

The answer is $\boxed{1}$.

The missing number is the number that, when added to the other two numbers, gives the sum of $10$.

The first number is $3$. The second number is $7$. When we add $3$ and $7$, we get $10$. Therefore, the missing number is $1$.

Option A, $3$, is incorrect because $3$ is already one of the numbers in the question.

Option B, $0$, is incorrect because $0$ does not add up to $10$ when added to either of the other two numbers.

Option C, $1$, is correct because $1$ adds up to $10$ when added to either of the other two numbers.

Option D, $7$, is incorrect because $7$ is already one of the numbers in the question.