为什么吃食性鱼类需要投饲配合饲料，而滤食性鱼类不需要？
（）可作电动机的过负荷保护。 ["热继电器","熔断器","自动开关瞬时过流脱扣器","定时限电流继电器","自动开关长延时过流脱扣器"]
The condition where a ship on the end of a tow line is riding a wave crest at the same time as its tug rides a wave crest is known as riding in（）. ["synchronism","harmony","check","ste"]
简述病状类型中的流脂或流胶。
为什么不同厂家生产的配合饲料营养指标相近，但养殖效果差异很大？
烟用物资的采购有哪几种形式？供应商是如何产生的？
