A:所有化学物质内部都存在化学键
B:共价键存在于原子之间,也存在于分子之间
C:离子键是阴、阳离子之间的相互吸引力
D:化学键通常指的是相邻的两个或多个原子间的强烈的相互作用
He s____at home last night.
在△ABC中,∠A,∠B,∠C的对边分别为a,b,c,如果c=2a,∠B=45°,那么∠C等于( )
我们经常看到某些糖尿病患者每天要在自己腹部上“打针”,他们注射的药物是( )
读问句,选择对应的答句。
____①What's the weather like today? A. No, you can't.
____②Where are my books? B. Yes, it is.
____③What time is it? C. It's rainy.
____④Can I wear my new skirt? D. It's twelve o'clock.
____⑤Is it cool? E. They're on the bed.