–Do you know this boy?He works really___.–Yes, I can ___ see him play. He always studies. 

Please don’t drop litter _______, you should throw it into the dustbin _______.

 --- _____do you study for a test?---By reading the textbook.

 My grandfather walks _____  than my grandmother.

I enjoy reading very much. When I read books, I feel that time goes     .