“ =0”是“（x₁，y₁）、（x₂，y₂）、（x₃，y₃）三点共线”的（　　）

In 2000, we ____ to the Great Wall and had a good time there.

在各项均为正数的数列$\left\{a_n\right\}$中，对任意$m,n\in N*$都有$a_{m+n}=a_m·a_n$．若$a_6=64$，则$a_9$等于（ ）

C

    Do you like traditional Chinese paper-cutting? Ding Xiang, a student at Nongsishi Middle School in Xinjiang, is really good at it. At the eighth National Excellent Talents Competition last month in Beijing, the 15-year-old girl got the gold award（金奖） for her paper-cutting skills.

    At the competition, Ding cut a piece: Millennium Dream（千年梦想）. The piece has two papers. One shows an ancient cave painting(壁画) and the other a Chinese-made spaceship. The two papers form a sharp contrast（对比）. Ding said she wanted to show three things with the piece: China's long history, China's rapid development, and her hope for the future of paper-cutting. This piece helped Ding walk away with the gold award.

    "I was very surprised to get the award." Ding said in an interview with Yili Daily, a Xingjiang newspaper. "I should thank paper-cutting for bringing me the award."

    All the hard work has paid off. In two years, Ding's skills have improved a lot, and she has the gold award to prove(证明) it.

    Ding said she has learned a lot from paper-cutting. "I have learned to observe things carefully," Ding told Yili Daily. "I have become more confident, too. It is a great help in my studies. Also, I have learned a lot of history from the art."

小华在书房听录音学习文言文，妈妈在客厅看电视，为了不受电视声音的干扰，小华应采取下列中较为合适的措施是（　　）