The word “they” in paragraph 1 refers to

Câu hỏi: Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate correct answer to each of the questions.
Scientists know that there were wolves on Earth about one million years ago. Dogs, on the other hand, have not been on Earth nearly as long. The oldest dog remains, found in Germany, are about 14,000 years old. Scientists have proven that dogs are descended from wolves. Though wolves and dogs share some of the same genes, they are not exactly alike. In fact, there are as many differences as there are similarities between the two.
First, there are physical differences between the two. Wolves have longer legs, larger feet, and a broader skull than dogs. They also walk differently from dogs. A wolf runs on its toes with its heels raised
up from the ground. This is more similar to a cat's walk than a dog's.
Second, there are mental differences between the two. Dogs have been domesticated. This means that dogs have been brought under the control of humans in order to provide companionship. Wolves have not been domesticated. They are wild animals. Having a dog as a pet is like having a juvenile wolf. A young wolf will turn into a mature adult, while a young dog does not mature. A dog might seem smart by performing tricks for people. Wolves need to be smart to survive in the wild. While it may not be impossible
to have a wolf as a pet, scientists are of the opinion that a wolf could never be domesticated in the same way as a dog.
It's important to keep in mind that the differences between the two are great, and each should be appreciated in its own habitat or home.
(Source: Paul Edmunds, Nancie McKinnon, Developing skills for TEOFL iBT)
The word "they" in paragraph 1 refers to
A. wolves
B. dogs
C. scientists
D. both wolves and dogs