[判断题]封闭火区时,应当合理确定封闭范围,必须指定专人检查甲烷、氧气、一氧化碳、煤尘以及其他有害气体浓度和风向、风量的变化,还必须采取防止瓦斯、煤尘爆炸和人员中毒的安全措施。( )
A.正确
B.错误

The origin of the almighty dollar is in what is now the Czech Republic. In 1519 ,a silver mine near the town of Joachimstal literally "Joachim’s valley," from the German Tal, meaning valley began minting a silver coin called, unimaginatively, the Joachimstaler. The coin, which was circulated widely, became better known by its clipped form, the taler. In Dutch and Low German, the initial consonant softened to become daler. English adopted this form, eventually changing its spelling to the modern dollar.
In the American colonies, there was no standard currency. The coin that was in widest use was the Spanish Peso, known also as" Pieces of Eight" because it could be divided into eight pie-like pieces. The English colonists informally assigned the name dollar to this coin. In 1785, when the Continental Congress established U.S. currency ,they adopted dollar as name for the standard unit of currency ,at the suggestion of Governeur Morris and Thomas Je
A. both US and England have used dollar as the name of their official currency
B. the Bank of England used" dollar" coins as currency for just a short period of time
C. the origin of the $ sign of the dollar is quite unimaginable
D. there are few countries in the world that have adopted an official currency named the dollar