2. (10 points) From the integers 1 to 10, at least ( ) numbers must be taken to ensure that there are two numbers whose sum is 10.
A. 4
B. 5
C. 6
D. 7
【Analysis】10 natural numbers are: $1, 2, 3, 4, 5, 6, 7, 8, 9, 10$; those that sum to 10 are $(1,9), (2, 8); (3, 7); (4, 6)$; the sum of the two numbers in these four pairs is 10. According to the pigeonhole principle, consider the worst-case scenario: taking out 6 numbers, which are the numbers $5, 10$ and one number from each of the four pairs. Taking out any additional number will result in two numbers whose sum is 10, according to this, the problem can be solved.

【Solution】Solution: From the 10 integers from 1 to 10, those that sum to 10 are:
$$
(1,9), (2, 8); (3,7); (4,6);
$$

Consider the worst-case scenario: taking out 6 numbers, which are the numbers $5, 10$ and one number from each of the four pairs. Taking out any additional number will result in two numbers whose sum is 10, i.e., $6+1=7$ (numbers),

Answer: At least 7 numbers must be taken to ensure that there are two numbers whose sum is 10. Therefore, the answer is: $D$.