问两道高中英语题1.i walked as far as ___ Eighth Street where i found

问两道高中英语题
1.i walked as far as ___ Eighth Street where i found the post office
A a B an C the D /
2.My brother took ____ interest in drawing ___ horses.
第一道题我选了B,我的想法是：走了一条和第八大街一样长的路,答案是D,原因说路名上的序数词不加冠词,这并没有解决我的问题,我的想法和做法错在哪?
第二题,答案是 an / 我想问interest是可数名词吗?
谢谢啦