The sign  means “_____”.

每天供给地球光和热的太阳与我们的距离非常遥远，它距地球的距离约为150000000千米，将150000000千米用科学记数法表示为（　　）

①不同的人可以采取完全相同的学习方法，别人怎么学我也怎么学

②只要能让我们学起来更愉快、更有效率，就是好办法

③我们只有在探索尝试、不断努力的过程中，才能找到适合自己的学习方法

④学习方法要根据自己的学习习惯，结合老师的教学实际来确定

关于机械能，下列说法正确的是（　　）

    My family came to America from China many years ago. I was born in Oakland in 1989. Many young Chinese Americans don't learn much1because our parents2us to learn English very well.

    Chinese is a difficult language. If we don't speak it3, it's easy to forget. Writing is hard, too. We have to remember lots of words and thousands of characters (汉字). In English, there are only 26 4.

    At home, I5English with my family. But now, we speak some Cantonese (广东话) because we watch films 6 that language.

    My mom has come to love F4, a Chinese boy band (组合). They are in the film Meteor Garden (《流星花园》). We all7the TV series, and we learn Cantonese8 saying some funny words from the TV series to each other.

    It's fun to speak Cantonese with my Chinese friends. It 9funny because we can't say the words just right.

    Young Chinese Americans know that our culture (文化) is getting lost, so we try to10something.