【单选题】There are three wastewater pollution sources in a certain area. The quantity and concentration of wastewater are shown in the table. The standards of COD, BOD and SS are 10 mg/L, 5 mg/L and 50 mg/L, r...
【简答题】There are six e_____________ exits on this aircraft, which are l__________ in the front, the rear and the middle of the main cabin. The s_______ instruction card is in your seat pocket. Please read it...