▲Sitting and talking to old friends “坐着和老朋友交谈”是一个整体行为，故谓语动词用单数。
▲当作主语的两个并列的动名词表达一个整体意义时，谓语动词用单数；若表达个体意义时，谓语动词用复数。如：
(1) Singing and dancing is inbred in children. 小朋友很喜欢唱歌跳舞。（“唱歌跳舞”是整体意义）
(2) Dancing and singing were among her many accomplishments. 她多才多艺，能歌善舞。（侧重“既能唱歌，也能跳舞”）