Look!Mr White together with some children ( )up shells on the beach .(pick) 请问主语到底是谁?

Look!Mr White together with some children (is picking )up shells on the beach .(pick)
主语是Mr White together with some children
但是这里有together with 用就远原则 谓语的单复数按照Mr White来定 所以用单数
希望能够帮到楼主