The word "it" in paragraph 3 refers to____________

Câu hỏi: Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 30 to 34.
Some people think that a spider is an insect, but it is an arachnid. Arachnids have two main body parts and eight walking legs while insects have three main body parts and six legs. Many insects can fly, but spiders cannot fly.
There are many different kinds of spiders around the world. They come in different colors, such as black, brown, white, yellow, and orange. Spiders usually live for one year but a spider called the Tarantula lives as long as 20 years. Some spiders are very small but some are so large they can fit a dinner plate.
The most unusual thing is that a spider can spin a web. Spiders have silk in their stom ach and they use the silk to make a web. The web is the spider's home. But the spider does not stick to its own web because its legs have oil on them. It is very strong and sticky. The web is used to catch insects. When an insect is trapped on a spider's web, the spider wraps the insect in silk. It eats the insect at a later time. However, the spider does not really eat it. Since it has no teeth, it puts venom in the insect to make it a liquid.
The word "it" in paragraph 3 refers to____________
A. a spider
B. the web
C. their stomach
D. an insect