Answer: 

`1` Russia is bigger than any other country in the world. (big)

`=>` Russia is the biggest country in the world.

`2` Many people believe that no sea in the world is warmer than the Red Sea. (warm)

`=>` Many people believe that Red Sea is the warmest sea in the world.

`3` The Nile is longer than any other river in the world. (long)

`=>` The Nile is the longest river in the world.

`4` No ocean in the world is deeper than the Pacific. (deep)

`=>` The Pacific is the deepest ocean in the world.

`5` Mount Everest is higher than every mountain in the world. (high)

`=>` Mount Everest is the highest mountain in the world.

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strucs: (so sánh nhất)

`+` ngắn:

`->` S + tobe/V+the + adj -est + in/on/of + place

`+` dài:

`->` S + tobe/V + the + most+adj+ in/on/of+ place

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by: @fionayewwmint (@khanhnhu2k12)

`1,` Russia is the biggest country in the world.

`2,` The Red Sea is the warmest sea in the world.

`3,` The Nile is the longest river in the world.

`4,` The Pacific is the deepest ocean in the world.

`5,` Mount Everest is the highest mountain in the world.

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`-` So sánh nhất `-` ngắn: (so sánh giữa 1 người/vật với nhiều người/vật)

`->` S `+` tobe/V `+` the + adj/adv `+` -est + in/on/of + place..

`-` So sánh nhất `-` dài: (so sánh giữa 1 người/vật với nhiều người/vật)

`->` S `+` tobe/V `+` the `+` most `+` adj/adv `+` in/on/of `+` place