喷墨打印机的工作原理是将溶解在打印墨水(pH：7.5~9.0)中的染料喷到打印纸(pH：4.5~6.5)上，形成不溶于水的固体。下列有关叙述正确的是(    )

关于声现象，下列说法中正确的是（　　）

一个几何体的三视图如图所示，这个几何体是（　　）

读短文，掌握其大意，然后从A、B、C、D四个选项中选出一个可以填入相应空白处的最佳答案。

    Have you ever planted a few trees on Tree Planting Day? Each year, millions of people, both  1 , plant a lot of trees. But this may not be the best way to make your home a  2 place.

   Last week we visited a park in Hebei. We were  3  to find most of the trees had been burned. The workers told us that the trees   4   soon after they were planted because they weren’t watered well enough.   5workers burned them and cleaned the place for   6  trees to be planted this year.   7  a card found in one of the dead trees, a student wrote, ＂I hope this tree will grow up with me to   8   the backbone(栋梁) of our country.＂The workers said that the survival(存活) of the trees was really more important than  9   trees were planted.

    Some people in Beijing now have a new idea that they can donate(捐赠) some money and let professionals (专业人士) plant and  10  the trees.

阅读下文，回答问题

    在求知的过程中，我们还要善于把勤学好问和观察思考结合起来。北宋有个大科学家，名叫沈括。他小时候读白居易的诗《大林寺桃花》：“人间四月芳菲尽，山寺桃花始盛开。”他想：为什么同是桃花，开花的时间相差这么远呢？他去问妈妈，妈妈说：“兴许是花开花落，有早有迟吧！”妈妈的回答没能解开沈括的疑团，他仍然把这个问题放在心上。有一次，他随大人到深山的寺庙里去，发现那里的温度要比山下低得多，才明白了其中的道理。