The time and effort he has devoted during the past few years trees in that remote area is

问题补充：

The time and effort he has devoted during the past few years trees in that remote area is now considered to be of great value.

A. plant

B. planting

C. to plant

D. to planting

答案：

A. plant

B. planting

C. to plant

(答案→)D. to planting

解析：考查非谓语动词。devote … to …致力于，to为介词，故选D。