第三人称单数做主语时,谓语动词用单数,至于主语后面的动词的形式,就是要看这个动词是否做谓语了啊,是谓语的话用单数,不是谓语的话具体情况具体分析.
e.g.Jane likes music.主语jane是第三人称单数,所以谓语like加s
Mary looks forward to receiving your letter.主语mary是第三人称单数,所以谓语look加s,后面还有一个动词receive,按照look forward to doing的用法,加ing