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. (C). From $\mathrm{C}_{3}^{1} \mathrm{P}_{2}^{2} \mathrm{P}_{3}^{3}-\mathrm{C}_{2}^{1} \mathrm{P}_{2}^{2} \mathrm{P}_{2}^{2}=28$ we get.