H1N1 flu from spreading our government has taken some effective measures.A. Prevent B. P

问题补充：

H1N1 flu from spreading, our government has taken some effective measures.

A. Prevent

B. Preventing

C. Prevented

D. To prevent

答案：

A. Prevent

B. Preventing

C. Prevented

(答案→)D. To prevent

解析：本题的含义为我们的政府采取了一些有效的措施以防止H1N1禽流感蔓延，表示做某事的目的用动词不定式to do作目的状语，故本题选D。