降钙素是一种多肽类激素，某科学机构为了研究一种新型降钙素，从预期新型降钙素的功能出发，推测相应的脱氧核苷酸序列，并人工合成了两条DNA单链，两条链形成部分双链DNA片段，再利用Klenow酶补平，获得双链DNA，过程如图．在此过程中发现，合成较长的核苷酸单链易产生缺失碱基的现象．分析回答下列问题：

如果一个正四面体的体积为9dm³，则其表面积S的值为____．

根据问句，选择合适的答句。

①Does Jane have a soccer ball?____              A. OK.

②Do you have a baseball bat?____                B. It's in my bedroom.

③Let's go!____                                             C. Yes, she does.

④Where's your baseball?____                        D. No, I don't.

⑤Is it under the teacher's desk?____              E. Yes, it is.

我们每天都需要用水，水是怎样来到我们家里的呢？请根据提示写一写。
Water comes into our homes
    Water⑴comes from the rain. It⑵____. The water is not clean (干净的）there. We can't drink it. It must⑶____.The water factory makes it clean. Then it⑷____.It comes out from the tap. We use water to⑸____.

“事物的存在取决于我们的感觉”，该观点属于（    ）