牙膏的主要作用是()。
A.消除口腔异味
B.摩擦清除菌斑
C.洁白美观牙齿
D.预防龋齿
E.预防牙周病
参考答案:B
Life of Pi is about an Indian boy who finds himself drifting in ________ Pacific Ocean with _______ Bengal tiger after ________ shipwreck.
A.the, a, a
B./, a, the
C.the, a, the
D./, the, a
在窄而深的房间中,采用下列哪种侧窗时采光均匀性最好
A.正方形窗 B.竖长方形窗C.横长方形窗 D.圆形窗