＿＿＿＿being March 12th they planted trees on the hill. A. ThatB. It isC. It　　　D. This

问题补充：

＿＿＿＿being March 12th, they planted trees on the hill.

A. That

B. It is

C. It

D. This

答案：

A. That

B. It is

(答案→)C. It

D. This

解析：it在此指时间,与being March 12th 构成独立主格结构，在句中作状语。