Read the following passage and choose A, B, C, and D to answer the following questions

Many people like to keep pets. Dogs and cats are very popular pets. Some people, however, keep birds or goldfish. They need less space and are easier to look after.

If you want to have a pet, you can buy one from a pet shop but you must be careful not to buy a sick animal. It is best if you know something about the pet you want. This helps you choose a healthy pet. However, if you do not have much money and know very little about animals, you can visit the Royal Society for the Prevention of Cruelty to Animals (RSPCA).

The first society for the Prevention of Cruelty to Animals was founded in England in 1821. It was set up to make sure that all animals are treated with kindness. The RSPCA in Hong Kong carries out this aim. The RSPCA officers collect animals which have no homes and are left in the street. They look after them until they are healthy again. People visiting the RSPCA may choose their pets from these animals and you can be sure that you will get a healthy pet. If later your pet becomes ill, you can take it to the doctors at the RSPCA for treatment.

When you have a pet, it is very important that you look after it properly. You must remember to feed it at suitable times. You should also give it a clean and comfortable place to rest. Your pet will be happy and healthy if you love it and care for it properly.

A snail's shell is ______________in form. A. theory B. pyramid C. spiral D. mysterious