A smile costs __________, but it gives so much. So we should learn to smile.
A:nothing
B:something
C:anything
D:everything
我国古代科技一直处于世界领先水平.其中既然在发明过程中体现“变废为宝”的环保理念,又对文化的交流和保存提供了重要条件的科技成就是( )
make up one's mind; give in; ever since; be fond of; grow up: on schedule; change one's mind ;care about; prefer to; get sb. interested in