对虾之所以叫“对虾”,是因为:() ["成对游玩捕食","过去常成对出售","双双百年偕老","捕捞时成双成对"]
它吃野猪,又不敢轻举妄动,悄悄跟着野猪走,好像在放牧野猪,当地人称之为“野猪倌”。这种虎是:() ["华南虎","新疆虎","孟加拉虎","东北虎"]
蜘蛛的食物是各种昆虫、蜈蚣、马陆、蚯蚓,甚至小鸟,其独到的捕食方法是:() ["咀嚼","吞食","舔食","吸食"]
单吊杆起货机一般有()台绞车。 ["A.1","B.2","C.3","D.4"]
液压起货机的手动液压操纵机构可随时用()方法向低压侧系统补油。 ["A.手摇泵","B.辅泵","C.蓄能器","D.低压油箱"]
请简述换热设备结垢产生的后果。