Visitors to the hills are greeted by signs        them to look out.
#89693
A
warn
B
to warn
C
warning
D
warned
推荐题目
_________, the experiment is sure to succeed.
#90652
A
If carefully doing
B
If carefully done
C
If it done carefully
D
If it doing carefully
 ____a living, she had to work from morning till night.
#93992
A
To make
B
made
C
Making
D
To have made