I have two elder brothers,______in the army for ten years.

I have two elder brothers,______in the army for ten years.
A the elder of whom serving
B the older having served
C the older of which served
D the elder one has served
为什么选B啊?
1.选A是定语从句的用法.但是该定语从句缺少谓语啊,serving不能单独做定语从句的谓语.
2.选C也是定语从句,served也可以单独做谓语,但是先行词是人,而关系代词which却只能指代物.
3.选D就更错了,等于两个是并列句,但是前后两个并列句之间却没有and这样的连词来连接.
4.所以答案选B.这是独立主格结构,做该句的状语.
该语法较为复杂,不予详述.相信楼主能慢慢明白!