Choose the sentence that best combines each pair of sentences given.

So many animals are now in danger of extinction. Then, a list of them is kept in a Red Book.

We can no longer remember having advised you on how to decrease your energy use.

We remember having advised you on how to maintain your energy use.

We remember having advised you on how to decrease your energy use.

We remember to have advised you on how to decrease your energy use.

Carbon dioxide is the only greenhouse gas that causes global warming.

Global warming results in greenhouse gases, including carbon dioxide.

One of the main greenhouse gases that lead to global warming is carbon dioxide.

Global warming causes greenhouse gases, including carbon dioxide.

Deforestation and loss of habitat threaten many species so that they will become extinct.

Many species lost their habitat because of deforestation and now they are extinct.

Deforestation and loss of habitat are driving many species to the verge of extinction.

Many species are extinct, so they run the risk of deforestation and loss of habitat.

The environment has been made catastrophic by global warming.

It is true that global warming is a catastrophe caused by the environment.

It has been proven that global warming is harmful to the environment.

The environment has been truly dangerous because of global warming.

People are totally unaware of the dangers of plastic bags to the environment.

People are fully aware of the dangers of plastic bags to the environment.

The dangers of plastic bags to the environment came to the attention of only a few.

It is time that people were aware of the dangers of plastic bags to the environment.

Numerous catastrophic consequences result in climate change.

Numerous catastrophic consequences result from climate change.

Climate change results from numerous catastrophic consequences.

Numerous catastrophic consequences cause climate change.

Global warming can’t be controlled by planting trees.

Planting trees is the only way to control global warming.

Planting trees can accelerate global warming.

Planting trees can help reduce global warming.