阅读下面短文，从每题所给的A、B、C和D四个选项中，选出最佳选项。

                                                                                                           C

    Every year, hundreds of millions of Monarch Butterflies(黑脉金斑蝶) from Canada and the United States journey as far as 2, 500 miles to the forests of Michoacan, Mexico, a place which has the world's largest insect migration(迁移). It's such a breathtaking sight, but as always, human greed is threatening to destroy it.

    The Monarch Butterflies start to arrive in Michoacan in late October to make their winter home in the trees high up in the mountains of the natural reserve. Once there, they gather together in large masses. These masses often become so heavy that they cause tree branches to bend or even break. But there's a purpose of all these massing — it allows the butterflies to survive in the low nighttime temperatures at these high altitudes.

    The Michoacan Monarch Butterfly Sanctuary is most impressive during the months of February and March, just before the winged insects begin their long journey home.

    Mexico's Butterfly Forest is a shelter protected by law, and one of the country's most popular sights, but that hasn't stopped people from slowly but steadily destroying it.

    Illegal woodcutting in the heart of the Monarch Butterfly Biosphere Reserve has been a longstanding problem, but criminals are rarely brought to justice. They are often set free after paying some money.

    Just last month, an even greater threat rose in Michoacan's butterfly home.  The country's largest mining corporation gained the right to reopen an old mine in the heart of the monarch reserve. Experts believe that if the mine is reopened, it will likely spell the end of this magical place.

    And as if all this wasn't bad enough, the increasing use of herbicides（除草剂） in the American corn belt has led to the decrease of  a plant which is essential to the monarchs' development from egg into butterfly.

I gave him a book as a(n) present.

    "Olyvia, love is simple. You don't have to do much to make someone happy. "That was what my mother said to me when I was a child. Over a year ago, I had a chance. My good friend Kaylee told me about her t____ to a small town called Gary, and how it was a life-changing experience. I made up my mind to go there myself.

    When I told my parents about the decision, they didn't a____ at first. They said I didn't know much about the place. They were worried that it was not s____ for me to go there. Thankfully, after I explained my plan to them in detail, they said yes.

    When our group arrived in Gary, I noticed how different the town was from where I lived. There were few stores or restaurants in the town; most had closed. So you would be very l____ if you could find a place to buy food or drinks. Houses were built on small hills. Many of them had broken doors or windows. My job was to help the local people to r____ houses.The work days were long and hot, but it was really good to see the houses taking on a new look day by day.

    The children there were also different. They seemed to enjoy every moment in life though they were poor. The smallest things would make these kids happy. I couldn't find words to describe their j____ when they received an ice-cream, a ball or even a kiss. The community was like a big family. Everyone knew each other and was there when someone needed help.

    I am so glad that I had this unforgetable experience. I truly learned the m____ of what my mother said. You don't need to do much to make a difference to others' lives.