________ you were busy, I wouldn't have bothered you with my questions.
此题为省略 if 的虚拟条件状语从句， 其结构为 had+主语+过去分词+句子其它，主句结构为： 主语 + would had done。
【句意】 如果知道你忙， 我就不会问问题打扰你了。