it was so dark outside that he---go out alone. A.dared not t

答案选A
解析：首先排除C,因为主句it was so dark outside 是一般过去式,主句和从句的时态要一直的,而C一般现在时.
其次在这里最好用dare 作为实义动词“敢---“的用法.dare to do sth 敢做某事!dare not to do sth不敢做某事.