I will use all of my efforts to develop myself to the best of my ability.

A) I

B) my

C) myself

D) my, myself

Have you done all of the problems by yourself?

A) Have

B) yourself

C) you

D) you, yourself

We must defend ourselves because no one else will.

A) ourselves

B) one

C) We

D) We, ourselves

She taught herself how to play the piano.

A) Herself

B) How

C) She

D) Piano

The children enjoyed playing with sand by themselves on the beach.

A) The

B) ON

C) Themselves

D) Children