下列关于我国基本国情的叙述，正确的是（  ）

①我国地域广阔，区域发展不平衡   ②我国发展成就举世瞩目，已成为发达国家

③我国资源总量大，人均资源充足   ④我国人口众多，人口、资源、环境矛盾突出

如果细胞核内存在DNA解开双螺旋的现象，则此时细胞可能处于（   ）

家用电磁炉以其高效、节能成为新一代智能灶具，小明在家中关闭其他所有用电器，在只有电磁炉正常工作的情况下．请你回答下列有关问题：

完形填空。
    Hello. I'm Jenny. I have a best friend.   1 name is Amy. We are in the same school. We both can sing and dance well. She is as  2 as me.
    At school, my teachers all can make 3   happy. But we must4  white blouse with the long sleeves. I am good 5   maths and English. She 6  English. She thinks it's difficult. Yesterday we7   a party at school. We enjoyed ourselves.
    At spare time, my favourite8   is winter. I like 9  snowmen in winter. But she likes eating ice creams in summer. What a pity!
    In two months' time, we are going to go to middle school. We are very busy every day. We  10   harder than now.

一支铅笔的价钱相当于一个练习本价钱的3倍，小红买了2支铅笔和5个练习本．一共用去了4.4元．一个练习本和一支铅笔各多少元钱？（用方程解）