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1.We are unable  to see the stars in the sky.Light pollution occurs.(makes)
........Light pollution makes us unable to see the stars in the sky.............................................................
2.Glass panels ,windows,lawns and roofs make light pollution worse.They reflect both artificial and sun light.(because)
.........Glass panels ,windows,lawns and roofs make light pollution worse because they reflect both artificial and sun light.........................................................
3.All sounds are not noise.Noise is any sound that is unwanted and goes beyond its certain limit,for example , above  80 decibels.(because)
.............All sounds are not noise becasue noise is any sound that is unwanted and goes beyond its certain limit,for example , above  80 decibels...............................................
4.More and more noise is  created by modern civilization.It has now become a major environmental pollutant,especially in urban areas. (so)
......More and more noise is  created by modern civilization, so It has now become a major environmental pollutant,especially in urban areas........................................
5.Contamination in the air happens.There is acid rain which damages soil , vegetation and aquatic life of the region .(causes)
............Contamination in the air causes  acid rain which damages soil , vegetation and aquatic life of the region .............................................
6.Noise pollution is one of the major causes of stress and anxiety.People  suffer from stress and anxiety.(because of )
...............Because of noise pollution,people  suffer from stress and anxiety  ..........................................

12.a

13.d

Câu 12:

A. 4,62 m

Câu 13:

D. Mai, Hoa, Hùng

12.A

13.D

Đánh giá giúp mình ạ,cảm ơn

Câu 3: B

Câu 16: A

b: \(S=2\left(1+2+2^2+2^3\right)+...+2^{2007}\left(1+2+2^2+2^3\right)\)

\(=30\left(2+...+2^{2007}\right)⋮30\)

S = 2 + 2² + 2³ + .... + 2²⁰¹⁰

S = ( 2 + 2² ) + ( 2³ +2⁴ ) +... + ( 2²⁰⁰⁹ + 2²⁰¹⁰ )

S = 2 . ( 1 + 2) + 2³ . (1 + 2 ) + ...+ 2²⁰⁰⁹ . ( 1 + 2 )

S = 2 . 3 + 2³ . 3 + ... + 2²⁰⁰⁹ . 3

S = 3 . ( 2 + 2³ + ... + 2²⁰⁰⁹)

Vì 3 chia hết cho 3 

=> S chia hết cho 3