and was tied up with work when I came back

因为工作的缘故,我回来的时候真是太累了。这里是“疲劳,疲倦”的意思；与。。。密切联系;忙於1。 系住He tied up the horse and went into the inn。他系住马,走进了小酒店。2。 使受阻The traffic had been tied up for three hours。交通阻塞已有三个小时。