我国下列地区生态环境也很脆弱的是[ ]
A．青藏高原
B．海南岛
C．云贵高原和广西的西北部石灰岩分布区
D．四川盆地紫色土分布区
AC
Where's my book? I looked for it _______ but I can't find it _______ . [ ]
A. somewhere, some where
B. anywhere, somewhere
C. everywhere, anywhere
D. anywhere, any where
下列哪种疾病不引起牙本质过敏症（）
A.磨耗
B.龋病
C.牙髓钙化
D.楔状缺损
E.牙折
