The doctor said that the valve in his heart is sick and needs surgery.

I check the clock every hour.

He used dynamite to blast the rock.

She was wearing a new bracelet on her wrist.

He was crossing the railway.

The centromere is a part of the chromosome and plays an important role during cell division.

She is good at playing the guitar, isn't she?

This furnace is very efficient.

Mom, will you make tea for me?

He proposed a new theory about the problem.