解释：在人活动范围内的水就污浊，在野外无人地方的水就清洁。同为一样的水，都是从天边开源，有的混浊有的清洁，这是它们所处环境使它们这样的。
购买旧书，它们的词与新词相同，也可以去图书馆。
The future of energy is low-carbon, but oil and gas will remain part of the mix for decades to come.
做伟大的事情很困难，但指挥伟大的事情更困难。
The key to speed reading is not reading faster, but understanding faster.
The future of construction lies in smarter, greener solutions.
外交需要克服短期利益的诱惑，着眼于长远利益和全球发展。
All I desired was to walk upon such an earth that had no maps.