10. 5 people participate in 4 groups, each group has two people, and each person must participate in at least one group. Then, the number of different groupings is ( ).
(A) 135
(B) 130
(C) 125
(D) 120
10.A.
5 people can form $C_{5}^{2}=10$ pairs. Every 4 pairs are called a grouping method. A valid grouping method should include all 5 people. Since fewer than 4 people cannot form 4 pairs, all invalid grouping methods, i.e., those containing only 4 people, total $\mathrm{C}_{5}^{4} \mathrm{C}_{6}^{4}=75$ (each 4 people can form $\mathrm{C}_{4}^{2}=6$ pairs). Therefore, the number of valid grouping methods is $C_{10}^{4}-C_{5}^{4} C_{6}^{4}=135$.