题目

在各项都为正数的等比数列中，首项，前三项和为21，则=（   ） A.33              B.72               C.84                D.189 答案：C 根据下面短文，用括号内所绘动词的适当形式填空。 My aunt is an engineer in America．She __1__（work）in the Company of Microsoft since 1986．Last month she __2__（come）back to China．We were very happy to see her on May Day．After we finished lunch，we showed her around our hometown． “This hotel __3__（build）last year．Look，the workers __4__（put）up another one over there．” “What a great change!” aunt said． “We __5__（plant）more trees and flowers in the town soon．And we'll do something to stop the factories from __6__（pour）the waste into the river．” I told her． Aunt was very pleased with what she saw．When we asked her __7__（stay）longer，she answered，“No，I can't．I must __8__（fly）to Beijing tomorrow．I have an important lecture to give．If I __9__（have）time，I'll certainly come back again．Though I live in America，I'll always be Chinese．I should do something for our hometown．Let's __10__（make）contribution to it together．