The central heating system of this offic
问题:
The central heating system of this office building is down and several workers ______ it right now.
A.had repaired
B.have repaired
C.repaired
D. are repairing
The central heating system of this office building is down and several workers ______ it right now.
A.had repaired
B.have repaired
C.repaired
D. are repairing