题目

硫酸亚铁晶体（FeSO4·7H2O）在医药上作补血剂。某课外小组测定该补血剂中铁元素的含量。实验步骤如下： 请回答下列问题： （1）补血剂存放时间较长会氧化变质，对滤液中铁元素的存在形式提出如下假设：         假设1：只有Fe2+                     假设2：只有Fe3+         假设3：                         。 （2）如何证明步骤①滤液中含有Fe2+                                              。 When we are unfamiliar with something, we may feel nervous and fearful. The help of others is a good 　35 to help us pull through. 　 I write for a big newspaper, and I wanted to 36 a story about parachute jumping（跳伞）. To make it a realistic as well as exciting story, I decided that I had to make a jump myself 　37 . Unluckily, I’m not good at any sport, let alone（更不用说）parachute jumping. 　 My friend Mr. Smith was willing to give me a 　38 . He took me to a ground school. The first day’s 　39 included several hours of instruction but not my first drop from an airplane. For this, I had to wait until the following morning. 　 The next morning, I was taken to the airfield. There, a heavy parachute was put on my back. Then I was asked to make my way to a small plane which had just stopped slowly on the runway. Once on board, the plane was soon 　40 . I began to feel nervous. As we reached one thousand meters, Harry, my teacher, hooked（钩）a 　41 from my parachute to a steel（钢制品）ring inside the plane. The line was to pull my parachute 42 after I jumped. 　 “Get ready, Henry,” Harry said. I moved carefully to the door. I wanted to cry, “NO, no, no!” But no word came. 　 “Jump!” Harry called loudly. “Jump!” Away from the plane, and down, down I fell, arms stretched. It worked! All at once I was very happy. Then I felt a quick 　43 . My big parachute had opened! It was the best 44 I ever had. I looked down. There were rivers, trees, fields and houses. I heard the soft sound of the air. This was fun. 35. A. way 　　　　　　　　 B. chance　　　　　　　　　　　　　 C. idea　 　　　　　　　　　 D. value 36. A. tell　　　 　　　　 B. write　　　　 　　　 C. read　 　　　　　　　　 D. copy 37. A. secretly　　 　　 B. instead　　 　　　　　　 C. finally　 　　　　　　　 D. first 38. A. try　　 　　　　　 B. hand　　　　 　　　　 C. gift　　　 　　　　　 D. suggestion 39. A. jumping　　 　　 B. journey　 　　　　　　 C. training 　 　　　　　　 D. entertainment 40. A. slowing　 　　　　 B. climbing　 　　　　　 C. landing　 　　　　　　　 D. filling 41. A. bag　　　 　　　 B. steel　　　 　　　　　 C. line　　 　　　　　　　 D. seat 42. A. light　　 　　　　　 B. broken　 　　　　　　　　　　 C. fixed　　　 　　　　　 D. open 43. A. comfort　 　　　　 B. wind　　　 　　　　 C. pull　　　 　　　　　 D. push 44. A. failure　 　　　　 B. experience 　　　　　　 C. competition 　　　　　 D. danger