是who is in the park，此处who做主语，谓语用单数，例如：
1、His argument presupposes that it does not matter who is in power.他的论点前提是谁掌权都无关紧要。
2、Who is in the chair today?今天谁主持
3、This is an easy routine， designed for anyone who is unused to exercise.这是一套简单的固定动作，是为不常锻炼的人设计的。
