题目内容：

The U.S. has countless secret swimming holes throughout most states, many of which you've likely never heard of unless you're from the area.

Havasu Falls (Arizona)	This attractive waterfall in the Grand Canyon is undoubtedly a destination spot requiring a 10-mile walk to the falls. You can take a guided tour to the falls, or make it on your own. The Havasu Falls are on the Havasupai Indian Reservation, which means you'll need to get a permit to visit — this has become increasingly difficult as more people discover this hidden place.
Hamilton Pool (Austin)	Hamilton Pool was created when an underground river's roof fell down suddenly; exposing what is now the swimming hole and creating a 50-foot waterfall that flows over the above limestone(石灰岩). You'll have to reserve beforehand to gain entry to the Hamilton Pool Preserve.
Chutes and Ladders (Maui)	To get to this secret swimming hole, you'll have to take a rope 40 feet down the face of a cliff, and then climb down about 8 feet of lava rock to the pool. Once there, however, you'll be glad you made the journey. The swimming hole is on the edge of the ocean — a natural pool, you could say — with a depth that invites you to jump in without crowds of people around to watch.
Homestead Crater (Utah)	The Homestead Crater is hidden under a rock dome(圆顶) with an opening at the top that allows for sunlight and air. It was once only accessible by that top opening, but there is now easy access through a side path for visitors. Go for a swim in this beautiful mineral water spring.

 

 

1.People need an official written statement to visit _________.

A. Havasu Falls    B. Hamilton Pool    C. Chutes and Ladders    D. Homestead Crater

2.What do you need to get to Chutes and Ladders?

A. A tour guide.    B. An invitation.

C. More outdoor skills.    D. Reservation in advance.

3.Which of the following can best describe the four places?

A. They are hidden in remote areas.    B. They are shaped by limestone.

C. They are created by local people.    D. They are accessible through a hole.