We prefer to have payment in US dollars. It may be difficult for us to do so.
我们用美元付款。用人民币支付可能有些困难。
Then, all of a sudden, it became cloudy and began to rain.
可是突然天就变了,乌云密布并下起雨来。
Those planning a trip to remote areas, or intending to live in countries where drinking water is not readily available, should know about the various possible methods for making water safe.