【题目】The water supply has been cut off temporarily because the workers ____ one of the main pipes.
A.had repaired
B.have repaired
C.repaired
D.are repairing

【答案】D
【解析】句意：水供应被暂时切断了，因为工人们正在修其中的一根主水管。水供应被切断是因为工人们正在修主水管，故用现在进行时。选D。