Snow has obliterated surface features and the sky is covered with uniform，altostratus clouds. There are no shadows and the horizon has disappeared. What is this condition called? （） ["Ice blink","Whiteout","Water sky","Aurora reflectio"]
基肥的作用有哪些？如何正确地施用基肥？
人们为什么要重视仪表？
During the watch at sea, where situations occur in the machine apace which may affect the speed maneuverability, power supply or other essentials for the safe operation of the ship（）should be informed as soon as possible. ["the chief engineer","the master","the bridge","the company superintendent"]
继续教育的途径有（） ["小学新教师试用期的培训","职务培训","骨干教师培训","高一层次的学历培训"]
怎样选择苗圃地？
