科学上鉴别死细胞和活细胞,常用“染色排除法”,例如,用台盼蓝染色,死的动物细胞会被染成蓝色,而活的动物细胞不着色,从而判断细胞是否死亡。所利用的是细胞膜的哪种功能( )
Look ___ the mess. A. /B. atC. to
-- What is he doing? -- ___ . A. He draws a picture. B. He is read a book. C. He is listening to music.
-- What are you eating? -- ___ . A. I eat some sweets. B. I’m eating some sweets. C. I eating some sweets.
-- Are you writing a letter? -- _____ . A. Yes, I do. B. No, I’m not. C. No, I don’t.
-- Are you eating some sweets? -- ___ . A. Yes, I am. B. No, I don’t. C. Yes, I do.