10. A. with which是"介词+关系代词"结构,常用来引导定语从句.with有"用"的意思,介词之后只能用which,不能用that. with which在定语从句中作状语,即he is writing with a pen.
11. C. in front of which 即in front of a farmhouse. In front of which在从句中作状语.
12. D. with whom引导定语从句.with whom放在从句中即为:my father works with the engineer.
13. D. whose引导定语从句,在从句中作主语family的定语.
14. A. that引导定语从句,因为先行词是all,所以只能选用that引导.
