Trees should be planted everywhere possible. Trees absorb carbon dioxide, a greenhouse gas.

A. Biodiversity has its own economic importance, so protection of biodiversity is important.

B. Biodiversity has its own economic importance that protection of biodiversity is important.

C. Protection of biodiversity is so important that biodiversity has its own economic importance.

D. Protection of biodiversity is important to make biodiversity have its own economic importance.

A. We will not know where all our rubbish goes.

B. We should know where all our rubbish goes.

C. We did not know where all our rubbish goes.

D. We will never know where all our rubbish went.

A. The lecturer said that in China, waste was growing twice as fast as the population.

B. The lecturer said that in China, waste is growing twice as fast as the population.

C. The lecturer said that in China, waste has been growing twice as fast as the population.

D. The lecturer said that in China, waste had been growing twice as fast as the population.

A. He said his girlfriend that he had bought a ring.

B. He said his girlfriend that he bought a ring.

C. He told his girlfriend that he had bought a ring.

D. He told his girlfriend that he bought a ring.

A. Emily said that we were staying in tonight.

B. Emily said that they were staying in tonight

C. Emily said that we were staying in that night.

D. Emily said that they were staying in that night.

A. She said that they had been to work the day before.

B. She told that they had been to work the day before.

C. She said that they had been to work the following day.

D. She said that she had been to work the day before.