1-It took me nearly 40 minutes to ride here.-Have a drink.pl

1-It took me nearly 40 minutes to ride here.-Have a drink.please.You___be thirty.
1-It took me nearly 40 minutes to ride here.
-Have a drink.please.You___be thirty.A,will B,must C should Dcan
2I don't fell___.The doctor asked me to go and see him__ three days
A.well every B well each
3-Did you build a bigger subway in this city?
-Not yet,But we____
A.do B.did C.are going to D didn't
3题为什么答案是C，be going to 可以放在句末不用加的别的成分？
选择说明理由