老师：Hello, everyone. Welcome back. Last time we followed Robin to visit different places online. Do you still remember? Well, we have visited online. I give you the pictures for hints. Yes, we have visited Beijing in China and we've visited New York in the USA. And we've visited different parts. For example, we've visited Tiananmen Square, the Palace Museum, the Summer Palace and the Great War in Beijing. And we've talked about Wall Street times, well, Central Park and Broadway in New York, right? And I have another question to ask you. What did we use to have the own tools online? That means the online tools. I give you some pictures for help. Did we use money? Did we use a computer? Did we use a passport? Do you know passport? We can use a passport to travel between countries.
老师：You may feel the meaning of the word. I think it's obvious. We only used a computer to have the tours online, right? Because online tours can help us save money and save time.
老师：Okay, now let's come to the two questions here. Well, have we visited online? And what did we use to have the tools? Let's read and compel. Pay attention to the red words. Actually, they represent different tenses. The first sentence represent the present perfect tense, while the second one shows us the simple past tense.
老师：Right? Now today we will have a special online tour. We will visit the Grammar Kingdom. After the visit we will know what it is about and how to use the grammar rules and the reason why we should learn the part grammar now.
老师：First, let's read three pairs of sentences here and try to tell the differences between them. The first pair, Daniel went to Beijing two years ago and Daniel has lived in Beijing for two years. I have a question. Can we find out where Daniel is now? According to the two sentences here, as for the first one, we cannot find out where Daniel is now. We can just know where Daniel was two years ago, right? As for the second one, we can say Daniel is in Beijing now. As for the sentence, we can find out Daniel started to live in Beijing two years ago, and now he still lives there.
老师：Now we can work out the rule. We use the simple past tense to tell what happened in the past, and we use the present perfect tense to talk about an action that started in the past and continues to the present.
老师：Now let's come to the second pair. Daniel bought a new computer last month. Daniel has bought a new computer. My question is, does Daniel still have the computer? Now, as for the first sentence, we are not sure. We can just know he bought it last month. As for the second one we can find. Daniel has a new computer now, but we don't know when he bought it.
老师：After reading the two sentences, we can work out the rule like this. We use the simple past tense to
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