C1 Simon is writing about Mars. Rewrite the defining relative clauses in simple sentences with the preposition with or in.
1 Mars is a planet that has an environment similar to that of the Earth.
2 Astronauts who wear space suits and helmets might stay on Mars for hours.
3 It is difficult to breathe on a planet that has much thinner air than that on the Earth.
4 On Mars there might be people who carry air tanks on their backs.
1 Mars is a planet that has an environment similar to that of the Earth.
2 Astronauts who wear space suits and helmets might stay on Mars for hours.
3 It is difficult to breathe on a planet that has much thinner air than that on the Earth.
4 On Mars there might be people who carry air tanks on their backs.
答案：1 Mars is a planet with an environment similar to that of the Earth.
解析：原句中“that has an environment...”是定语从句，可转换为“with an environment...”作后置定语，“with”表示“具有”。
2 Astronauts in space suits and helmets might stay on Mars for hours.
解析：“who wear space suits and helmets”可转换为“in space suits and helmets”，“in”表示“穿着，戴着”。
3 It is difficult to breathe on a planet with much thinner air than that on the Earth.
解析：“that has much thinner air...”转换为“with much thinner air...”，“with”表示“具有”。
4 On Mars there might be people with air tanks on their backs.
解析：“who carry air tanks on their backs”转换为“with air tanks on their backs”，“with”表示“带有”。
解析：原句中“that has an environment...”是定语从句，可转换为“with an environment...”作后置定语，“with”表示“具有”。
2 Astronauts in space suits and helmets might stay on Mars for hours.
解析：“who wear space suits and helmets”可转换为“in space suits and helmets”，“in”表示“穿着，戴着”。
3 It is difficult to breathe on a planet with much thinner air than that on the Earth.
解析：“that has much thinner air...”转换为“with much thinner air...”，“with”表示“具有”。
4 On Mars there might be people with air tanks on their backs.
解析：“who carry air tanks on their backs”转换为“with air tanks on their backs”，“with”表示“带有”。
C2 Simon is interested in stories about aliens. He even writes to aliens. Replace each of the underlined parts in his letter with another expression.
Dear aliens,
Humans are thinking about moving to another planet
(1) because the pollution on the Earth is very serious. Many people
are in no doubt (2) that life on Mars would be very interesting, but I am
not sure. We could not play football on Mars (3) because of the low
gravity. Life would be boring for me (4) if I could not play football. Maybe
this problem could be solved by building special indoor playgrounds
(5) which have the same football fields as those on the Earth.
By the way, would strangers be welcome? I hope to hear from you soon.
Simon
答案：
(1) because of the serious pollution on the Earth
(2) about the interesting life on Mars
(3) because the gravity is low
(4) without football
(5) with the same football fields as those on the Earth