關於幾題多益文法題 - 自學

請問下列這三題
因為實在不懂為什麼是這答案
所以請懂的人為我解說一下
1. The job of an arbitrator is ____ disputes between two or more parties.
A. settled B. to settle C. being settle D.settler (Ans. B)

2. The plan to advertise on national television had to be dropped due ___costs.
A. to increase B. to increased C. increasing D. being increased
(Ans.B)

3. Pooling resources is one way for small companies ____ a presence in the research and development field.
A. to maintain B. maintaining C. maintained D. maintain
(Ans.A)

謝謝^^

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