1.Those children are tired.
2.Their mother is tired,too.
3.That ice cream man is very busy.
4.His ice creams are very nice.
5.What's the matter,children?We are thirsty.
6.What's the matter,Tim?I am tired.
其中1,4,5题的主语是复数形式,用are.
2.3题的主语是第三人称单数形式,用is.
6题的主语是I,我,第一人称形式,第一人称一般现在时用am.