A group of dogs are known as therapy dogs.这种a group of... a committee of...到底是用单数还是复数呢？
A group of 后面接复数名词。"A group of + 复数名词" 作主语时，谓语动词用复数或者单数都可以。如：
A large group of people were waiting for him at the airport. 一大群人在机场等候他。（摘自《韦氏高阶英汉双解词典》p.934）
A select group of scientiats has been invited to the conference. 一群科学家精英已受邀参加会议。（同上）
a committee of 后面接复数名词。如： a committee of experts 专家委员会 （摘自《牛津英语搭配词典》第2版 committee 词条）
