---Why were you late for school today?

----It was ________ I help catch a thief on the bus.

A．since

B．as

C．for

D．because

企业采用计划成本核算原材料，平时收到原材料时应按实际成本借记“原材料”科目，领用或发出原材料时应按计划成本贷记“原材料”科目，期末再将发出材料和期末材料调整为实际成本。( )