[单选题]
97.18: A motorist travels 400 km at 80 km/h and 400 km at 100ulrj 8pp/mj67 c/ y.sc km/h. Whawa1/xti2k 95/xfl /c8nxbxd yocy wl2p )x86nt is the averf56idyp / c28wl/8lnxx )1t/xxckwo y9b xna2age speed of the motorist on this trip?
A. 84 km/h
B. 89 km/h
C. 90 km/h
D. 91 km/h
E. 95 km/h