在反应3Fe+2O₂Fe₃O₄中，Fe，O₂，Fe₃O₄三种物质的质量比为（　　）

（C）

    I think that I am very lucky because I have a lot of friends. My best friend is Mai. She is 16 years old. She is 2 years older than me. We live in the same village. She is my neighbor and we are now classmates, so we have been friends for so long. Mai is tall and thin. With long black hair, she has got an oval(椭圆形的) face with big bright eyes, a high nose and a small mouth. Mai is very beautiful, especially when she smiles.

    She is always helpful, polite and honest（诚实的）. When her friends have difficulties, she always tries her best to help them. Although we have the same hobbies and interests, we have different personalities（个性）. I am sociable and enjoy telling jokes. My classmates think that I'm rather outgoing(外向的). Unlike me, Mai is quite serious and prefer quietness to noise. However, we can keep secrets together, so we are close friends. Mai is one of the best students in my class and she works hard. I like doing homework with her. She always tries her best to help me with my studies. I think as time goes by, our friendship will be deeper and deeper.

下列有关输血与血型的叙述错误的是（    ）

下表为元素周期表的一部分，针对表中①～⑥元素，回答下列问题

（1）①元素在周期表中的位置是第二周期　 ____　族．

（2）②和⑤两种元素中原子半径较大的是　 ____　（填元素符号）．

③和④两种元素的最高价氧化物对应水化物中碱性较强的是　 ____　（填化学式）．

（3）写出③的单质在⑥单质中燃烧的化学方程式 ____