首先whattheyeatandthewaytheycooktheirfood这部分作为differentin中in的介词宾语.whattheyeat和thewaytheycooktheirfood相互间是并列句,and是用来连接这两个并列句的.whattheyeat可以忽略不看,他是完整的并列从句中的一句完整句.

　　假设用你选定的B,填入句中,...differentinthewayinthattheycooktheirfood.inthat能充当从句中的什么角色呢?从句动词cook的宾语已经有了,是theirfood,inthat的that也是宾语,和theirfood重复了,冲突了,所以不能用B.