51.（ ）

(单选题)—Don’ t put the waste on the ground, young man.—Oh, I’ m sor (单选题)Now the Great Wall has become one place of the ______ not on (单选题)This school is not only for the children ______ first langua (单选题)With my glasses ______, I will have to buy a new one. (单选题)So little ______ about science that the lecture was ______ m (单选题)John thinks it won’t be long ______ he is ready for his new (单选题)We Chinese people are very ______ our long history. (单选题)These flowers need special care ______ they can live through (单选题)After retiring, he was recommended to ______ gardening as a (单选题)At last, we decided to go swimming instead of ______.