正在生产中的国产大型客机C919部分机身采用了新型的铝锂合金，这种材料具有较高的强度和适宜的延展性。铝锂合金中的铝(Al)元素与锂(Li)元素的本质区别是（       ）

阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处

填入一个适当的词或使用括号中词语的正确形式填空。

    Hey, my name is Sydney Roberge. I'm 13 years old and I ____ (life) in the USA. I'm fun and outgoing. I like all ____ (kind) of music and love to sing every day. My dream is ____ (be) famous for my singing one day. I don't care ____ you are black or white. My favorite sport is football. I love animals, and my favorite animal is a cat.

      I'd love to chat with someone who is ____ (young) than 18 and older than 13. I'm very open and I'm looking for a friendship. I plan to move to the UK ____ Ireland when I turn 18, so I'd like to talk to someone from those parts of the world, but it ____ (real) doesn't matter where you are from as long as you are ____ (friend).

    Here is a ____ (describe) of what I look like and a little more about ____ (I):

    E-mail address: uklover 42 @yahoo.com

    Well, anyway, I can't wait to hear from you!

某二倍体植物染色体上的基因B₂是由其等位基因B₁突变而来的，如不考虑染色体变异，下列叙述错误的是（　　）

—Is this _________ computer?

—Yes, it is.