The United Nations had meetings where world leaders agree on what to do about global warming. If there is too much pollution in the air, some people had health problems.
Ecologists looked for special spots on white pine trees to know if there
were high levels of ozone.
Many types of air pollution are invisible, but some can saw with the naked eye.
The teacher asked the boys if they did the task.
Satellite images proved that deforestation
increased rapidly.
The passage is so difficult that I could understand it.
Experts said that less than 3 per cent of the water on Earth was fresh water.
His health has improved since he returned from the hills.
If we had sorted the waste, we sawed millions of kilowatts of energy.
Объяснение:
Write the verb in brackets in the correct form.
The United Nations (have) meetings where world leaders agree on what to do about global warming. If there is too much pollution in the air, some people (have) health problems.
Ecologists looked for special spots on white pine trees to know if there (were) high levels of ozone.
Many types of air pollution are invisible, but some can (be seen) with the naked eye.
The teacher asked the boys if they (had done) the task.
Satellite images proved that deforestation (was increasing) rapidly.
The passage is so difficult that I (can not) understand it.
Experts said that less than 3 per cent of the water on Earth (was) fresh water.
His health has improved since he (returned) from the hills.
If we had sorted the waste, we (would have saved) millions of kilowatts of energy.
