最好能顺便多举几个例子,Not far from the club there was a garden,___ own

选B,因为只有逗号,没有连词连接,判断这是个非限制性定语从句,先行词为garden.
若要选A,须改成Not far from the club there was a garden and its owner seated in it playing bridge with his children.
若要选C,须改成Not far from the club there was a garden,of which owner seated in it playing bridge with his children.
不能选D,因为that指代garden,用在这里句意不通.
举例：He is the boy you just mentioned,whose father is a teacher.
=He is the boy you just mentioned and his father is a teacher.

应当选A。
这并不是一个定语从句。定语从句应当也具有一般句子的完整结构，而本句中，seated是一个形容词，用于be seated等结构。如果采用BCD三项，沿用定语从句结构的话，应当在seated前面加was，以使句子结构完整。
用A项，使得逗号后面的部分整体成为garden的定语，其中seated是its owner的状态。...

B,这是个非限定性定语从句，代所有格

B whose 这是个 形容词性从句， 后面的 从句是 修饰 garden 这个名词。