[单选] 风机盘管采用的电机多为（）调速电机。

共振型消声弯头是利用共振吸声结构来改善普通消声弯头对（）噪声消声效果较差的问题。 A.低频。 B.中频。 C.高频。 D.超高频。 Which statement concerning GMDSS Radio Operator requirements is FALSE（）. Each compulsory vessel must carry at least two licensed GMDSS Radio Operators at all times while at sea。 Each compulsory vessel must carry at least two licensed Radio Operators at all times while at sea and may elect to carry a GMDSS Radio Maintainer as well。 Communications involving safety of life at sea do not have to be logged as long as the compulsory vessel was not involved in such communications。 While at sea，adjustments to，and the maintaining of，GMDSS equipment may be performed by the GMDSS Radio operator as long as the work is supervised by an onboard licensed GMDSS Radio Maintainer。 班级精神文化的定义是什么？班级精神文化建设有哪些途径？ 华电《电力安全工作规程》（热力和机械部分）在检修工作中如需将盖板取下，应采取哪些防护措施？ 柜员发生现金差错时，应及时进行哪“三立一定”？ 风机盘管采用的电机多为（）调速电机。