The speaker appeared on the platform. The audience stood up and

The speaker appeared on the platform. The audience stood up and clapped warmly, (complex sentence)
【正确答案】：When/ As soon as the speaker appeared on the platform, the audience stood up and clapped warmly.
【题目解析】：根据以上两个单句的关系，我们将其第一句处理为时间状语从句When…或As soon as…，把第二句处理为主句。