For many years, Bruce Bexler dreamed of going to the lands no human had explored and discovered rare, unknown species. That might sound like an impossible dream, but Bexler turned it into a reality.

    In December 2015, he, together with a team of Australian and American scientists, adventured into a rain forest on the island of New Guinea. They were the first people ever to enter the region. “As we were dropped on the ground by helicopter, we found no trails anywhere; it was really hard to get around,” Bexler says.

    Within minutes of landing, the team spotted a black chicken-like bird. The scientists soon determined that the creature was a type of honeyeater-the first new bird species to be sighted on New Guinea in 60 years. The honeyeater wasn't the only surprise for them. They discovered more than 40 previously unknown plant and animal species. “We were like kids in a candy store?' Bexler recalls. “Everywhere we looked, we saw amazing things we had never seen before.”

    The new found species didn't shy away from the scientists. Two long-nosed echidnas even let the visitors pick them up and take them back to camp to study them. Bexler thinks the animals weren't scared because they had never seen humans before. He explains, “This area gives scientists a place where they can study the behaviours of animals that have not yet learned to be afraid of people.”

    Bexler and his team did not have enough time to study the area completely. “We just scratched the surface, Bexler says. “Anyone who goes there will come back with a mystery.”

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当使用管道煤气的用户改烧天然气后，在相同条件下燃烧等体积的燃气，理论上所获得的热值，后者大约是前者的（   ）

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