They do not know what (A.is in their stockings B in their st

应该选A.若问句当从句,应用正常语序.根据这个原则,乍一看is好像应放在最后才是陈述句的语序,但请注意该从句是对主语提问,对主语提问的疑问句语序和陈述句的语序是一样的,所以应是what is in their stockings.可以做个试验,把特殊疑问词what换成something,这句话就成了陈述句something is in their stockings,语序不变.