21.While riding a tiny boat across the Indian Ocean, the author _____.

A. volunteered to act as a pilot

B. felt regret about his decision

C. enjoyed the beautiful sunshine

D. talked with other people happily

22.The author probably wanted to know how the boatman _____.

A. kept fit in his spare time

B. spent his life on the boat

C. navigated his boat at sea

D. communicated with others

23.What was the purpose of the author's trip?

A. To see a whale shark.

B. To learn how to dive.

C. To swim the Indian Ocean.

D. To save underwater creatures.

24.How did the author feel after he jumped into the sea?

A. Rather anxious and angry.

B. A little scared but excited.

C. Doubtful and disappointed.

D. A bit tired but later relaxed.

History tells us that footwear was one of the first things ancient people learned to make. Footwear helped them across rocky paths or hot sands without injuring themselves. The earliest footwear we know of was simply a piece of plaited (编织的) grass or leather tied to the feet.

The ancient Egyptians seem to have invented the first footwear with a firm sole (鞋底) - sandals. Egyptian royalty usually wore sandals that had a different style from those with lesser status, while slaves were not allowed to wear anything on their feet. The sandal is still the basic form of footwear in many countries,