Buffett said the number of people who had agreed to sign on was at the high end of his expectations.这个句子people who had agreed to sign on这里不缺少宾语 宾语是 to sign on不定式作宾语 其中 sign on是动副词组 属于不及物动词 是 签订受雇合同的意思
was at the high end of his expectations是宾语从句中的系表 结构 不是which was at the end of his expectations 也不是which引导的宾语从句