7. Using the digits $0,1,2,3,4$ to form a five-digit number without repeating digits, the number of five-digit numbers where exactly one even digit is sandwiched between two odd digits is ( ).
A. 48
B. 36
C. 28
D. 12
7. From $C_{3}^{1} P_{2}^{2} P_{3}^{3}-C_{2}^{1} P_{2}^{2} P_{2}^{2}=28$, we get the result, so the answer is $C$.