问题
单项选择题
长臂卡环的近基牙的卡环体和卡环臂应位于（）.
A.均位于导线之下
B.均位于导线之处
C.卡环体位于导线上而卡环臂位于导线之下
D.卡环体位于导线之下，卡环臂位于导线之上
E.卡环臂距龈缘越近越好
答案
参考答案：B
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长臂卡环的近基牙的卡环体和卡环臂应位于（）.
A.均位于导线之下
B.均位于导线之处
C.卡环体位于导线上而卡环臂位于导线之下
D.卡环体位于导线之下，卡环臂位于导线之上
E.卡环臂距龈缘越近越好
参考答案：B
Passage Four
Why haven’t British government bodies initiated any studies
A．Because they do not take the problem of sleepy drivers on motorways as of great significance.
B．Because they have not been aware of the seriousness of the problem of sleepy drivers.
C．Because they have no figures on the number of accidents caused by drivers’ sleepiness.
D．Because they plan to support relevant researches or a general study on "driver behaviour".