His partner left the company it more difficult for him to run it.A makes B make C to mak

问题补充：

His partner left the company, it more difficult for him to run it.

A makes B make C to make D making

答案：

解析：本题应选非谓语动词，用现在分词作结果状语。现在分词做结果状语表示自然而然的结果，而不定式表示意料之外的结果。如：His parents died , leaving him an orphan.父亲去世了，（结果）他成为孤儿。Tom got to the station only to find the train had gone.汤姆到达车站，却发现火车已经开走了。