Having been attacked by terrorists，______．（ ）A. doctors came to their rescueB. the tall building collapsedC. an emergency measure was takenD. warnings were given to tourists

步骤 1：分析句子结构
句子的主干是“Having been attacked by terrorists， ______．”其中“Having been attacked by terrorists”是现在分词短语作状语，表示动作发生的背景或原因。现在分词短语的逻辑主语应该和主句的主语保持一致。

步骤 2：确定逻辑主语
现在分词短语“Having been attacked by terrorists”的逻辑主语应该是“the tall building”，因为大楼是被恐怖分子袭击的对象，而不可能是医生、紧急措施或者警告等。

步骤 3：选择正确答案
根据逻辑主语的确定，选择B项“the tall building collapsed”作为主句，表示大楼倒塌了。