A study showed how much dogs love their owners. In the experiment, the-researchers first /measured how many tears    1    (produce) by dogs when they were just spending time at home with their owners. The team then repeated the experiment, this time with dogs that were reunited with their owners    2    being apart for five hours. The results showed dogs only shed tears during the reunions. The team now wants to find out    3    dogs have a similar emotional response when reunited with other dogs.

Imagine that you’re sleeping in the wild in a tent and are awakened by the sound of wolves howling(狼嚎叫). That’s     1    happened to me last summer when my family and I spent the night at the Wolf Conservation Center (WCC) in South Salem, New York. The howling didn’t frighten me. Wolves howl to communicate     2    each other.

The WCC educates people about wolves,    3    (they) relationship to the environment, and how to ensure that they survive. Guests     4    (invite) to visit the wolves year­round. The center is home to twenty­five wolves and two    5    (serious) endangered species—the red wolf and the Mexican gray wolf. At one point, both species     6    (be) extinct in the wild. With help from the WCC, the wolves are making a comeback.

“Wolves help to keep all other animals in balance(平衡) and keep the environment really     7    (health) ,” said Mary Kate Kabbes, an educator at the WCC.

When wolves became extinct in Yellowstone National Park, the elk(麋鹿) population increased to five times its normal(正常的) size and destroyed areas where birds lived. As    8    result, several bird species were forced to leave the park.

Now that wolves are back at Yellowstone, the birds have returned. “Learning about wolves, reading books about them, and telling your family and friends is a simple way    9    (help) spread the word about the     10    (important) of wolves.” Kabbes said.