选哪个,为什么?it happened at about 6 o'clock yesterday evening,whe

选哪个,为什么?
it happened at about 6 o'clock yesterday evening,when i ___________from work.i was coming down station road,and just as i was walking past NO.38,i heard a noise.
a .come home b.was coming home c got home d was getting home
c和d的区别?
另外,a lot 的词性和用法,