7. As shown in Figure 1, A, B, C, and D are four oil wells in an oil field, and it is planned to build three roads to connect these four oil wells (each road connects only two oil wells). Therefore, the number of different road construction plans is ( ) kinds.
(A) 12
(B) 14
(C) 16
(D) 18
7.C.

The number of roads connecting any two oil wells is $\mathrm{C}_{4}^{2}=6$. Choosing 3 out of these 6 roads gives $C_{6}^{3}=20$ ways. However, road construction plans that only connect three of the oil wells are not acceptable, and there are $\mathrm{C}_{4}^{\mathrm{i}}=4$ such plans. Therefore, the number of road construction plans that meet the requirements is $C_{6}^{3}-C_{4}^{1}=16$.