∵复数2-i1+i=(2-i)(1-i)(1+i)(1-i)=1-3i2,
故选D.
The teaching building has five floors. My classroom is ________ the third floor. [ ]
A. on
B. in
C. at
D. to
制汤应选用新鲜的含可溶性营养物质和呈味风味物质较多的原料,营养物质通常指脂肪和()。
A.矿物质
B.维生素
C.蛋白质
D.碳水化合物