"Do you often go to this swimming pool?" Mai said to Nam.

• Mai wanted to know if Nam often went to that swimming pool.

Today is very cold, so we can't go for a walk in the park.

• If it weren't so cold today, we could go for a walk in the park.

Scientists began to fight against COVID-19 years ago.

• Scientists have been fighting against COVID-19 for years.

I am a more careful typist than Quang.

• I type more carefully than Quang.

Because of running fast, he could manage to catch the last bus.

• Because he ran fast, he could manage to catch the last bus.