a group of后面加（不）可数名词的单数还是复数啊?那它的谓语动词是应该用复数形式吗

a group of 后面一定是加可数名词,即使有时可能你认为不是复数形式,那也可能是这个词的单复数同形的A group of people are talking outside.A group of students playing on the playground.A group of workers are ...