His spirit is very strong.

He worked all night to finish the job he had begged for.

He passed away quietly.

General relativity is a theory of physics proposed by Einstein.

I was able to find the Big Dipper.

It is believed that black dwarfs are formed by the cooling of white dwarfs.

This square matrix has the same number of rows and columns.

The diagonal elements of this matrix are all 1.

He is a world-renowned biologist.

Observing dark nebulae is difficult.