单选题 To meet a government requirement, a bottler must test 5 percent of its spring water and 10 percent of its sparkling water for purity. If a customer ordered 120 cases of spring water and 80 cases of sparkling water, what percent of all the cases must the bottler test before he can send it out?
(A) 6.5% (B) 7.0% (C) 7.5%
(D) 8.0% (E) 8.5%