⑴Where are you?____                                                         A. I'm talking to my friend.

⑵Excuse me. Where is the supermarket, please?____        B. I'm behind the tree.

⑶Thank you.____                                                                C. Turn left.

⑷Where is the train?  ____                                                  D. It's at the station.

⑸What are you doing?____                                                E. You are welcome.

在“探究力和运动的关系”的实验中，让木块由静止开始沿斜面滑下，木块在三种不同水平面上运动一段距离后分别停留在如图所示的位置．

下列不属于湿地生态系统的生态效益的是（　　）

一电炉子的电阻R=2000Ω，通过的电流I=5A，通电10min产热Q=____J．