I can't find my sand eraser.

He became the champion of the mixed martial arts competition.

He is good at devising strategies for siege warfare.

Mr. Zhai is my best friend.

He was wrapping the present.

He was plucking flowers in the garden.

I saw a flock of sheep on the top of the mountain.

The Riemann sum is a method for approximately calculating the integral of a function.

He was singing to himself alone in the room.

Unable to bear the pain, he had no choice but to scream.