题目

Some things can carry(携带) messages, for example, a sign（标志） at the bus stop helps you to know which bus to take. Signs on the door tell you where to go in or out. Have you ever noticed that there are a lot of signs around you and that you receive messages from them all the time?People can communicate on many other ways. An artist can use his drawing to tell about beautiful mountains, about the blue sea and many other things. Books are written to tell you about all the wonderful things in the world and also about people and their ideas.Books, magazines（杂志）, TVs, radios（广 下列命题 (1)如果非零向量a与b的方向相同或相反，那么，a＋b的方向必与a、b之一的方向相同； (2)△ABC中，必有； (3)若，则A、B、C为一个三解形的三个顶点． (4)若a、b均为非零向量，则|a＋b|与|a|＋|b|一定相等． 其中真命题的个数为 [　　] A．0 B．1 C．2 D．3