—When ______ you born, David?

—I ______ born in 1995. [ ]

A. was; were

B. were; was

C. were; were

D. was; was

表层浮选是利用（）原理，将细粒硫化矿轻轻地撒在水流表面，疏水的硫化矿物漂浮在水面上，亲水的脉石下沉，从而达到分离。

A.物理化学

B.表面张力

C.物理吸附