In our modern world, when something wears out, we throw it away and buy a new one. The  36  is that countries around the world have growing mountains of  37  because people are throwing out more rubbish than ever before.

36．A．key    B．reason  C．project D．problem

37．A．gifts B．rubbish  C．debt D．products

36题的答案是 d。解题依据是什么