Soot blowers should be used in proper sequence so that（） ["excess stresses will not be set up in the boiler","the decks will not be covered with soot","the soot will be swept toward the uptakes","there will not be a loss of steam pressure"]
生产周期的长短与生产的（）有关。
Neap tides occur（）. ["At the start of spring，when the Sun is nearly over the equator","Only when the Sun and Moon are on the same sides of the Earth and are nearly in line","When the Sun and Moon are at approximately 90° to each other，as seen from the Earth","When the Sun，Moon，and Earth are nearly in line，regardless of alignment order"]
The valve that prevents water from backing out of the boiler into the feed line is the（）. ["bottom-blow valve","skin valve","feed-check valve","feed-stop valve"]
对330～500kV线路，应按什么原则实现主保护的双重化？
绘出异步电动机星形接线绕组接线示意图。
