...butLincoln's home in downtown Springfield,Illinois,(prove...
分析句子成分可知,设空处作谓语动词,Lincoln's home in downtown Spring-field Illinois作主语;结合句意及设空处后的时间状语从句 since it opened to the public可知,此处指过去发生的事情对现在造成的影响,符合现在完成时概念,故设空处用现在完成时;主语 Lincoln's home in downtown Spri...