單項(xiàng)選擇題吊頂工程的吊桿應(yīng)通直,吊桿距主龍骨端部距離大于()時(shí),應(yīng)增設(shè)吊桿。當(dāng)?shù)鯒U長度大于()時(shí),應(yīng)設(shè)置反支撐。

A.300mm,1000mm
B.600mm,1000mm
C.300mm,1500mm
D.600mm,1500mm