阅读理解。 'I swear, I didn't steal anything!' I shouted over the alarm. Obviously the security guard didn't believe me because he seized the shopping bag right out of my hand. 'Do you have a receipt for this?'he asked doubtfully, putting any new back-to-school outfit (全套装备) onto the dusty floor near the mall entrance. 'Of course I do,' I replied, fishing my wallet out of my coat pocket. Elsie and Monica, my two best friends, stood beside me. They were laughing their heads off! I almost tore my wallet apart for the receipt, but it  had disappeared.' Let me look again,' I said nervously. Then I looked again, and again, and again! My face was getting hotter by the minute and my heart was beating like a racehorse. Finally, I looked back at the guard and whispered, 'It's not here.' The guard picked up my clothes and said, 'You'll have to come with me, Miss.' When he opened the office door, I saw a man sitting  behind a big metal desk. It was the manager. Then I had an idea. 'May I say something?' I asked. 'I can prove I didn't steal this thing.' Then I explained all about the cashier (出纳员).She said that she had bought the exact same outfit as a birthday present for her little sister. 'We'll just see about that,' the manager said and went off to find her. Ten minutes later, I was free! It was terrible to be unfairly accused of something!Then I remembered shouting at my sister that very morning for taking my new hair clips. Had she really taken them?I made a promise that day never to accuse someone of something without proof, and I haven't. At least something good came out of my terrible experience. 1. Why didn't the security guard believe the author? A. Because she looked nervous at that time. B. Because she had no money in her wallet. C. Because her face turned red after being caught. D. Because she didn't have a receipt for the outfit. 2. That the author's two friends laughed their heads off showed________. A. they laughed at the author who stole things B. they didn't believe the author was a thief at all C. they expected the author to be caught D. they played a trick on the author 3. We can infer the author was very ______from the underlined part in Paragraph 4. A. nervous B. careful C. frightened D. excited 4. Who proved that the author hadn't stolen anything? A. The cashier. B. The manager. C. The author's friends. D. The security guard. 5. From her experience, the author learned that________. A. you should believe in yourself in face of difficulty B.  it is a terrible thing to be suspected by friends C. you should not doubt others if you can't prove it D. you should ask for a receipt for whatever you buy