设置天线的初始下倾角：在城区，应使天线的（）对准覆盖区的边缘；在郊区、农村、公路、海面等，应使（）对准覆盖区的边缘。
简述海底构造的环境效应。以印尼海道的关闭为例。
The marine diesel engine is a type of diesel engine used on ships The （） of its operation is not very difficult to understand. ["principle","principal","cause","case"]
请问决定最高开工率的要素有哪些？
The majority of medium speed and high speed marine diesel engines for main or auxiliary drive operate on the （） cycle. ["two-stroke","four-stoke","long-stroke","short-stroke"]
弧后扩张的模式有哪些？
