如图，在正三棱柱ABC﹣A′B′C′中，若AA′=2AB，则异面直线AB′与BC′所成角的余弦值为（   ）

材料化学是一门新兴的交叉学科，在新材料的发现和合成领域，材料化学作出了独特的贡献，下列关于各种材料说法不正确的是（　　）

下列说法正确的是（　　）

下列句子中标点符号使用正确的一项是（    ）

    My name is Alice I1a student. I get up at6:00 in the2I meet Cindy at school. "3are you?!" she asks. I say, "I'm4, thank you."

    At 8:30, I am in my class. Miss Li asks, "What is that in English?" I say, "It is 5cup." Then she asks, "Can you6it?"  "C-U-P," I say. Bob is 7friend. He likes listening to music (听音乐 ). He has anew8and he listens to9a lot. He can sing many songs10English and Miss Li asks him to sing one for us.