2 . Four Unique U.S. National Parks

This national park is the site of the longest known cave system in the world,which is really proper for a park called “Mammoth(猛犸象).” It’s the ideal place for an adventure lover, with about 400 miles of caves and tunnels to explore. One of the most popular sections to visit within the caves is called Frozen Niagara, a special part of the caves that looks like a waterfall frozen in time.

Even though it’s one of the least-visited national parks in the country, it’s definitely one of the best national parks in Florida. There’s no accounting for Dry Tortugas National Park’s amazing beauty. Located about 70 miles from Key West, this park is made up of several islands that feature blue waters and white-sand beaches, colorful marine life, and the historic Fort(堡垒) Jefferson, one of the largest 19th-century forts in U.S. history.

If you’re looking for interesting red and pink rocks, you can’t do better than Bryce Canyon. The national park is known for its fascinating rock formations and hoodoos(石林), as well as its starry skies at night. Some of the best places to visit in the park are the Natural Bridge, Fairyland Canyon, or any of the scenic viewpoints throughout the park.

It’s the hottest and driest national park in the country, but it’s also a place of beautiful desert views and interesting natural phenomena, like the sailing stones on the Racetrack Playa. Depending on where you are in the park the climate can be extreme — it’s home to snowy mountains, dry desert, colorful flower fields, and cool lakes. You might also recognize it as the planet of Tatooine from the original Star Wars movies.

4 . My mother turned ninety. I knew I needed to find a senior _______ center. Not for her — for me. If I were at her age, I would want to stay in shape to _______ life, getting a lot of pleasure. Yes, walking in local parks was my _______, but I wasn’t so active as before.

I called a nearby center, “Do you have aerobics (有氧运动) classes _______ for seniors?” “Sure. Come and check us out! We start at 10 am,” the receptionist (接待员) replied and _______. The next morning, I went there. One part of me was _______ that the class was too easy, not doing me any good. The other part feared it was too hard for me to _______.

When I came into the room, a woman _______ me, “Oh, you’re new. Welcome.” Then the music started. The hour-long workout woke up the muscles I didn’t often _______ in daily walks, suiting me fine. I became a member there. My classmates ranged in age from fifty to ninety. Most gave the exercises their own ________, doing as much or little as they could. ________ no one kept score. Soon I learned physical well-being wasn’t the only ________ there. During breaks, people chatted happily. Whenever some people were ________ we asked around. Were they busy? Were they in hospital? Moreover, we signed cards for those who were ill.

I ________ to be in good shape now as I’ve hoped. Still, I’m grateful for things more valuable from the class — close friendships and new social ________.