单项选择题 如果在房间的内壁饰以吸声材料或安装吸声结构，或在房间悬挂一些空间吸声体，吸收掉一部分（），则室内的噪声就会降低。A、直达声B、混响声C、宽频声D、低频声

单项选择题 汽车钣金件主要使用（      ）进行制造。 A、冲压模具 B、塑料模具 C、铸造模具 D、锻造模具

单项选择题 Which is talking about the contribution of research at the tactical and program-specific level?A.Research helps set organizational goals and policies.B.Research provides guidance with the short-term and specific marketing and operational decisions.C.Research assists the CVB staff in effectively managing their limited time and resources.D.Research helps formulate a destination’s tourism master plan.