Final answer:
The domain for the function 2x + 5 is all real numbers because there are no restrictions on the x-values for linear functions like this one.
Step-by-step explanation:
The student has asked what the domain of the function 2x + 5 is. The domain of a function represents all the possible input values (x-values) for which the function is defined. In the case of linear functions like 2x + 5, there are no restrictions on the x-values; the function is defined for all real numbers because linear functions are continuous over the entire real number line, and there aren't any values for which the function becomes undefined (such as division by zero or square roots of negative numbers).
Therefore, the correct answer to the student's question is B. all real numbers. In other words, you can substitute any real number for x in the function 2x + 5, and the function will still be valid. This particular function does not have restrictions such as division by zero or square root of a negative number that would otherwise limit the domain.