说起PTE口语，难题除了Repeat Sentence之外，同学们公认的最难的一道题就是Retell Lecture，这道题和听力联系的极其紧密，稍有不慎口语和听力将双双gg，做好Retell Lecture，听力分数才能有高分的可能。
Poisonous blue frog
So, it turns out the frogs like I mentioned before are incredibly diverse, so over 7000 species and many of them are nocturnal so they live, you know, they only come out at night but there are some that come out during the daytime and many of the ones that come out in the daytime have really bright colors and the blue frogs are the poison dart frogs is one type of blue. There are many blue frogs actually, but one type is called the poison dart frog and the reason they’re called that is because the native people in the Amazon who set in South America used to capture these and take little darts and roll them on the skin of the frog and they’d use that to shoot the monkeys out of the trees, and it’s because these frogs are incredibly toxic. They have neurotoxins on their skin, so they wear their armor basically on the outside of their skin. One of the things that makes frogs or amphibians different from other vertebrates is that they have special glands that produce defensive compounds, mostly toxins that if something tries to bite them they get the toxin in their mouths and then what happens to that predator is that their muscles stop working so they literally can’t bite and they stop breathing.
So, some of them are really dangerous actually and most of the ones that are dangerous are out in the daytime, so they’re flaunting their colours they have very bright either reds or blues or oranges and they’re basically showing off their poisonous nests in a sense.
Let me add to the complexity of the situation. We find ourselves in at the same time that we’re solving for climate change. We’re gonna be building cities for 3 billion people that’s doubling of the urban environment if we don’t get that right I’m not sure all climate solutions in the world will save mankind because so much depends on how we shape our cities not just environmental impacts but out social well-being, our economic vitality, out sense of community and connectedness fundamentally. The way we shape cities is a manifestation of the kind of humanity we bring to bear, and so getting it right is I think the order of the day and to a certain degree, getting it right can help us solve climate change because in the end, it’s our behavior that seems to be driving the problem, the problem isn’t free. But it’s not just the kind of sprawl you think of or many people think of as low-density development out at the periphery of the metropolitan area. Actually I think that sprawl can happen anywhere at ant density, the key attribute is that it isolates people, it segregates people into economic enclaves and land-use enclaves.
The future of city
The future of our cities, if we do it right, is gonna be super cool I mean. We’re talking about growing biological material as the literal foundation of a whole city we’re gonna get there through. We can live in a variety of different places so when you think of deserts you probably think like brown and Dead’s not great, but we could actually transform the Sahara into a pretty lush desert. NASA’s Goddard Institute for Space studies had laid out a plan to pump desalinated seawater from the coast into the Sahara, and it could use these pipes to irrigate fields of eucalyptus trees, as the trees took root they would replenish the soil and cause more rainfall which would then even more growth. Because eucalyptus survives well in heat and then it could be watered using those pipes. But over time they took root it would lower the Sahara’s temperature by 8 degrees Celsius bring clouds in because of increased humidity to reflect the sun’s rays back into space cooling it down a little more and the trees could capture 8 billion tons of carbon per year which would be amazing. Of course, there’s a few problems with this the main problem being that it cost like 2 trillion dollars that’s kind of a lot. We can even live underwater. It’s expensive but it is also possible the technology exists to create underwater colonies now for like a hundred people at a time. They used plans from like bunker like habitats but there are problems. You know you have different diseases when you live in closed environments like that. Not to mention you are not going to see as much of the Sun. So you’re gonna have problems with paleness and vitamin D production issues.