— You helped me with the heavy box. Thank you very much.
— __________.
考查交际用语。
I can't agree more 我非常赞同；That's not the case 情况不是这样的；That's not the point那不是重点；Don't mention it 别客气。根据第一句句意“你帮我拿了盒子，谢谢你”可知，答语表示没关系，故选D。
— I'm tired out after three-day work day and night.
— ______ relax yourself? Go out and enjoy the natural beauty.
考查疑问句。
why not +动词原形=why don't you +动词原形；what about+doing sth.；shall we do sth。根据回答中“出去享受大自然的美”，祈使句，主语是you。所以选A。