酒精温度计中的液柱随温度的变化而升降,这主要是因为 [ ]
A.分子之间有间隔
B.分子是构成物质的一种微粒
C.分子是由原子构成
D.分子是保持物质化学性质的最小粒子
答案:A
设x、y、z是空间不同的直线或平面,对下列四种情形:
①x、y、z均为直线;②x、y是直线,z是平面;③z是直线,x、y是平面;④x、y、z均为平面.其中使“x⊥z且y⊥z⇒x∥y”为真命题的是( )
A.③④
B.①③
C.②③
D.①②
根据语境和句意,从括号中选择一个可填入句子的正确选项,并将答案填写在答题卡上指定的位置。
小题1:The cook added salt into the soup but it still wasn’t_______ enough. (salt, salty)
小题2:The story book is interesting and it was______ by Mark Twain. (written, writing)
小题3:“What do people in Korea do when they meet _______the first time?” “They usually bow.” ( in, for)
小题4:Singapore has a night_______, you can watch many kinds of animals there.(zoo, party)
小题5:Every year, Guiyang attracts larger numbers of tourists, ______in summer.( especial, especially)