無(wú)線通信中通過(guò)電場(chǎng)、磁場(chǎng)之間不斷的能量轉(zhuǎn)換，電磁波得以從雙極振子向外傳播，電場(chǎng)和磁場(chǎng)的方向與傳播方向保持垂直。
1、正確正確
暫無(wú)解析
______,weareairmailingyouourlatestquotation-sheet.
WhichofthefollowingisnotmentionedasWTO'sobjective?
MoststormsoccurbetweenAugustandOctober,andearlySeptemberistheriskiestperiodfor______storms.
迫使尼克松總統(tǒng)下臺(tái)的事件是（）
Whichofthefollowingsentencesisthemostproper?______
