Ⅱ. Complete the passage with proper words or the correct forms of the words given.
I was walking in the Amazon rainforest with my guide. Suddenly, I heard 1. strange sound of water. It was a loud, bubbling noise, like a pot of boiling water.

Then I decided 2. (take) a look. A river was right in front of me, and it was boiling! I 3. (careful) touched the water with my hand. It was so hot 4. I pulled my hand back immediately.
This was amazing. At first, I wondered 5. the river was boiling because of the heat from the volcano. However, we were far away 6. any volcano. Why was the river so hot? How could it be boiling?
Local people 7. (know) about this river for a long time. But even scientists don't know exactly why it is so hot. Perhaps there are some chemicals under 8. (it) river bed. Maybe something special is heating the water from below.
I looked at the boiling water and felt so curious. Our world is full of wonderful 9. (secret) like this. This boiling river shows us that nature still has many wonders waiting to 10. (discover).

Ⅱ. 1. a 2. to take 3. carefully 4. that 5. if/whether 6. from 7. has known 8. its 9. secrets 10. be discovered