题目

己知元素X、Y同周期，且电负性X>Y，下列说法中一定不正确的是  A．第一电离能：Y<X  B．最简单气态氢化物的稳定性： HmY> HnX  C．最高价含氧酸的酸性：元素X对应酸的酸性强于Y  D．X和Y形成的化合物中，X显负价，Y显正价 答案：B Can dolphins talk? Maybe they can't talk with words, but they talk with sounds. Dolphins travel in a group. We call a group of fish a "school". They don't study but they travel together. Dolphins are mammals, not fish, but they swim together in a school. Dolphins talk to other dolphins in the school. They give information. They tell when they are happy or sad or afraid. They say welcome when a dolphin comes back to the school. They talk when they play. They make a few sounds above water. They make many more sounds under water. People can't hear these sounds because they are very high. Sometimes people catch a dolphin for a large aquarium(水族馆). So they can watch dolphin shows in the aquariums. Dolphins don't like to be in an aquarium, being away from their school. They are sad and lonely if they do so.There are many stories about dolphins. They help people Sometimes they save people's lives. Many people believe that dolphins can bring them good luck. 根据短文内容, 判断正（T）、误（F）.1.Dolphins can talk and show their feelings with sound.2.Dolphins make more sounds above water than under water.3.Dolphins' sounds are very high, so we can’t hear them.4.Dolphins will feel happy if they are away from their school.5.Dolphins can save people's life and may bring good luck.