Consider the following statements with reference to Frege.
1. Frege introduces a distinction between the reference and the sense of an expression.
2. Objects are what proper names stand for.
3. He invented the theory of quantification.
Which of the statement(s) given above is/are correct?

A. 1 and 2

B. 1 and 3

C. Only 3

D. All of these

Answer: Option D