劳动合同中的一些具体内容，如工作岗位．工作内容等，未在劳动合同中明确的，可采用订立专项协议（合同）的形式明确。专项协议的期限不得超过劳动合同的期限。

No sooner had he finished his talk       he was surrounded by the workers.

A．as

B．then

C．than

D．when