问题
选择题
Sustainable development is long-term ________which focuses on the environment and ________ natural resources.
A．plan; preserve
B．plan; preserving
C．planning; preserving
D．planning ;preserve
答案
答案：C
考查名词及动词。plan计划；planning n. 规划,计划,设计。focus on doing集中做，根据句意选C。