问题
单项选择题
Lines passed around the falls to hold the boat while passengers are boarding are（）.
A.life lines
B.frapping lines
C.tricing lines
D.tripping lines
答案
参考答案：B
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Lines passed around the falls to hold the boat while passengers are boarding are（）.
A.life lines
B.frapping lines
C.tricing lines
D.tripping lines
参考答案：B