4. Four students participate in a competition. The competition rules stipulate: each student must choose one question to answer from question A or B. Choosing question A, a correct answer earns 100 points, and a wrong answer earns -100 points; choosing question B, a correct answer earns 90 points, and a wrong answer earns -90 points. If the total score of the four students is 0, then the number of different score combinations for these four students is ( ).
(A) 18
(B) 24
(C) 36
(D) 48
4.C.
(1) If all four people choose A (or B), among them, two are correct and two are wrong, there are $2 \mathrm{C}_{4}^{2}=12$ ways;
(2) If two people choose A and two choose B, for each question, one person is correct and one is wrong, there are $2^{2} \mathrm{C}_{4}^{2}=24$ ways.

In summary, there are 36 different scoring situations for the four students.