The exam is difficult, so I want to ask for a postponement.

Due to the fire, black smoke was billowing in the sky.

Black smoke was rising from the scene of the fire.

Pi is approximately 3.14.

We are planning to hold a big banquet this weekend.

He restrained himself from expressing his opinion.

This commercial is very interesting, isn't it?

Citrate plays an important role in organic chemistry.

In chemistry class, I learned about basic oxides.

The number of visitors to the park today is higher than yesterday.