The engineers in this lab spent several weeks _______ their plan

The engineers in this lab spent several weeks _______ their plans for the new bicycle.
A、counting
B、stripping
C、elaborating
D、casting
【正确答案】：C
【题目解析】：count计数；strip拆卸；剥夺；修剪（树枝）；elaborate精心制作；详细阐述；cast投，抛；计算；浇铸。句意：这个实验室的工程师们花了几个星期的时间精心设计新自行车的计划。