He stayed up all night studying for the exam.

The London Underground is one of the oldest subway systems in the world.

He is good at spelling.

His behavior was absurdly ridiculous.

Using the private railway makes commuting very convenient.

That unsolved problem keeps him awake at night.

That unsolved case keeps him awake at night.

The process of name resolution is very important in computer networks.

It's important to believe in yourself.

She uploaded a selfie to Instagram.