I had a lot of presents on my birthday. But my mother gave me the best. It was an MP3 player. It was green with some decorations like stars, butterflies and flowers. Now I can listen to music. I can look at the time. I can even play some games with my MP3 player. It's very easy to bring it with me because it's very small. My MP3 is very special to me because it was my mother’s present and I think it's very pretty and usefull.

Tiến hành các thí nghiệm sau:

(a) Sục H₂S vào dung dịch nước clo.

(b) Sục khí SO₂ vào dung dịch thuốc tím.

(c) Cho H₂S vào dung dịch Ba(OH)₂.

(d) Cho Cu vào dung dịch H₂SO₄ đặc, nóng, dư.

 (e) Đốt H₂S trong oxi không khí.

(g) Cho Al₂O₃ vào dung dịch NaOH loãng, dư.

Số thí nghiệm xảy ra phản ứng oxi hoá - khử là

A. 5.                       

B. 3.                         

C. 4.                         

D. 6.

About once a week in the summer. I don't go swimming in winter.

Oh, and I think you should put this question in Unit 7: Your house