When will you return, sir/madam?

Tomomi helped renovate the house.

Studying the history of the Middle Ages is very interesting.

The tough base of this mushroom is very hard.

He is the champion of the stone, paper, scissors game.

We need mutual understanding.

He believes in 'an apple a day keeps the doctor away', so he eats fruit every day.

Research on xenotransplantation has the potential to open new frontiers in medicine.

This river has a lot of small stones.

This rock is a type called nepheline.