Assume whatever that is not sold domestically was exported, then which year has registered highest growth in exports of automobiles?

Total automobile production exported in the year 2004 = (800+500+475)-(700+450+300) = 325

Total automobile production exported in the year  2005 = (700+550+450)-(675+500+350) = 175

Total automobile production exported in the year  2006 = (1025+675+475)-(900+625+400) = 250

Total automobile production exported in the year  2007 = (1200+650+475)-(1050+600+375) = 300

Total automobile production exported in the year  2008 = (1250+600+350)-(975+550+350) = 325

From the data itself we can see that highest growth occurred in the year 2006. 

Therefore, we can say that option B is the correct answer.