【正确答案】 B

【答案解析】[解析]
An explosion in a Pennsylvania coal mine killed one worker Monday, but five other miners escaped. The blast went off 2,300 feet underground at the R＆D coal mine in Schuylkill County. Some officials say it appears a blast went off in the anthracite mine when workers detonated the explosives, but that's still under investigation.
The process right now is to continue the interviews and then get back down underground and complete the inspections and in that way we can complete the investigation as to what happened.
[8] But, the accident knocked out the ventilation system, making it too dangerous for investigators to go down into the mine shaft. Regulators ordered the facility closed until the investigation is complete.

本题的出题点在转折处(but)，题干的核心词是the investigation和dangerous。新闻提到，爆炸造成了地下通风系统损坏，使得调查工作异常危险，故选B。