问题
选择题
As they _____ in the snowstorm in the deep mountains, they had great _____ in getting in touch with
the outside world. [ ]
A. lost; trouble
B.were caught; difficulty
C. were stuck; difficulties
D. were trapped; troubles
答案
答案：B
随时间t变化的关系如图（b）所示.(g取10m/s2)
；