【单选题】The accelerating force of the wind on a small 200-kg sailboat is 707 N northeast. If the drag of the keel is 500 N acting west, what is the acceleration of the boat?
【单选题】TAIWAN STRAITS EAST GUANGDONG:CLOUDY TO OVERCAST WITH LOCAL SHOWERS WIND NE 22 TO 33 KTS SEAS ROUGH TO VERY ROUGH VIS 10 TO 20 KMS.The Vis. in this area is ______ nautical miles.