The answer is C: was waving. <em> Every</em> is a determiner and one of its purposes is to refer to all members of a group of three or more, but they are considered <em>individually</em>. Altought this word represents more thant one, still it takes a <em>singular verb</em>. Other examples are: Every worker <em>knows</em> the machine. Everybody <em>likes</em> parties. Every student <em>has</em> a schedule.