--Whydon'twesaveourselvesthetroubleandusethestairs,Ste...

問題詳情：

 -- Why don't we save ourselves the trouble and use the stairs, Steven? -- Come on! Man invented the lift so that we don’t have to act like cavemen.

     -- Ok, Steven, if you ______ insist on being lazy. A. can                         B. should                    C. shall                D. must

【回答】

D

知識點：情態動詞

題型：選擇題