若代数式x²+ax可以分解因式，则常数a不可以取（   ）

古城选址都很讲究，一般都依山傍水，城市布局也是依势随形，追求人工与自然的协调。如山东济南的老城，南依千佛山，市内泉群广布，汇入大明湖，形成“四面荷花三面柳，一城山色半城湖”的独特景观。城市布局追求人与自然的协调体现了
①发挥主观能动性与尊重客观规律和客观条件的关系
②城市布局要深刻地把握人与自然的联系
③城市布局要追求各自的个性
④依山傍水是城市选址应遵循的一般规律

任务型阅读

    Alex Smith， a fifteen-year-old boy， studied in an American boarding school (寄宿学校). In this school， students could go into town after school in the afternoon____

    One afternoon， Alex walked to the town. He looked about at the shops and then went to a cinema____It was eight o'clock. He was a little worried， He walked back to the school as fast as possible.

    When he arrived， he ran quickly to the main entrance (入口). It was locked. He looked up at the window of his dormitory(寑室). It was on the third floor. The window was open____But the door was also locked. Then he saw another open window on the first floor. It was the window of the teachers' office____Alex quickly climbed into the room. Just then， he heard someone opened the door. He had to hide under the sofa at once. One minute later， a teacher came in____Under the sofa Alex had to lie on the floor.

A．He looked into the room-no one was there. B．After the film was over， he looked at his watch. C．But they must go back to the school before six o'clock. D．The teacher turned on the light， sat down on the sofa and began to read a book. E. But it was quite dark and he went round the school building to another door.

在“探究灯泡的电功率跟哪些因素有关”时，同学们提出了如下猜想：
甲：电功率跟电压有关，电压越高，电功率越大。
乙：电功率跟电流有关，电流越大，电功率越大。
(1) 小文同学采用右边的电路来验证猜想甲，他选择串联电路的理由是____ ，从而达到控制变量的目的。

(2) 实验中小文除通过观察比较两灯泡的亮度来比较两灯泡功率的大小，还需要收集的数据是____ 。
(3) 探究出电功率跟电压和电流的关系后，爱动脑筋的小文猜想 ：“电功率跟电阻之间也可能有一定的关系。”于是，他向老师借了一些定值电阻和其他相关器材进行实验，其实验数据如表一、表二所示。
表一

R/Ω	5	10	15	20	30
I/A	0.2	0.2	0.2	0.2	0.2
U/V	1	2	3	4	6
P/W	0.2	0.4	0.6	0.8	1.2

表二

R/Ω	5	10	15	20	30
I/A	1.2	0.6	0.4	0.3	0.2
U/V	6	6	6	6	6
P/W	7.2	3．6	2．4	1.8	1.2

根据表一和表二中的数据，小文同学得出的结论是：电功率跟电阻阻值之间没有规律可循。
请你分析表一和表二后，对小文同学的结论进行评价和分析：____  。

钟面上3时整，时针和分针形成____；6时整，时针和分针形成____。