The correct answer is $\boxed{\text{(C) 23, 19}}$.
In this sequence, each number is 3 less than the previous number. Therefore, the next number in the sequence is 23, and the number after that is 19.
Option A is incorrect because 24 is not 3 less than 21.
Option B is incorrect because 22 is not 3 less than 19.
Option C is correct because 23 is 3 less than 26, and 19 is 3 less than 23.
Option D is incorrect because 29 is not 3 less than 32.
Option E is incorrect because 23 is not 3 less than 20.