【单选题】--When did your pen pal arrive _______ Beijing? --He got here_______ the morning of the 9 th of June.
【单选题】I _____ e-mails to my pen pal when Susan called me last night. [ ]
【单选题】在血管内皮细胞受损时,描述错误的是( )。
【简答题】PAL识别电路是怎样识别那行是NTSC行,那行是PAL行的?
【判断题】PAL—D解码器是专为解调PAL—D彩色广播而设计的。()