从Ａ、Ｂ、Ｃ、Ｄ四个选项中，选出可以填入空白处的最佳选项。
21. The manager of the company told us that very little ____ was made of the waste material in the past.
A. cost B. vale C. use D. matter
22．In many places in China, ______ bicycle is still ______ popular means of transportation.
A．a; the B./; a C．the; a D．the; the
