题目内容：

A sign can be found in the front yard of a house in the US. The people living here want to let their dog play outside and ensure it won’t run into the street. So, they hire a company to set up an “invisible fence”, an electric wire buried in the ground around the yard. The dog wears a special collar and when it walks near to the “fence”, the wire will send out a small shock. The dog quickly learns to stay away from the edge of the yard. As it says at the bottom of the sign, the fence will keep your dog “safe” (away from the street) and “at home” (contained inside the yard).

    The small word “BRAND” printed in blue means that “Invisible Fence” is registered as the company’s brand name. Similarly, the “TM” printed after “your dog safe at home” stands for “trade mark”, a slogan registered specifically to one company.

1. The people set up an “invisible fence” _________.

     A. to let their dog play outside their house

     B. to keep their dog away from the edge of the yard

     C. to keep their dog inside their yard

     D. to warn others not to enter their house

2. Which is NOT true about the “invisible fence”?

     A. The fence does not exist at all.

     B. The “Invisible Fence” is the name of a company.

     C. Without the special collar, the fence won’t work on the dog.

     D. Science and technology play an important part in it.

3.