第20题: [单项选择]Whenever your marine radio is on,FCC Rules require you to monitor(). A. a commercial ship-to-ship channel B. the last frequency that was used C. the distress and calling frequency D. the radio only if expecting a call 参考答案:C
第21题: [单项选择]药材半枝莲的特征是() A. 唇形科,表面黄绿色或微带紫色,节处紫色明显,有白色茸毛 B. 爵床科,茎呈方柱形,多分枝,节稍膨大 C. 唇形科,叶展平后三角状卵形或披针形,花单生于茎枝叶腋 D. 菊科,茎呈圆柱形,气芳香,味微苦 E. 报春花科,常缠结成团,叶展平后呈宽卵形或心形 参考答案:C