1.此题的关键是要弄清楚whoever/whomever引导的宾语从句(做介词to的宾语)中,whoever/whomever所充当的成分的区别.
2.该题的whoever=anybodywho;whomever=anybodywhom.
即该题可以变化成为:
Thewaiterinthatrestaurantalwaysgivethevacantseatsto(whoever/whomever)comesfirst.
=Thewaiterinthatrestaurantalwaysgivethevacantseatsto(anybodywho/whom)comesfirst.
=Thewaiterinthatrestaurantalwaysgivethevacantseatstoanybody(who/whomcomesfirst).
3.该问题也就转变成为who/whom在修饰先行词anybody的定语从句中所做成分的区别了.
很明显,该关系代词=先行词anybody,在定语从句中做____comesfirst的主语.
既然是主语,当然用主格形式who.
所以相对应的anybodywho=whoever.