火焰原子吸收光度法中，空气-乙炔火焰适于低温金属的测定。
参考答案：对
5x（x2﹣2x+4）+x2（x+1）的计算结果是[ ]
A．6x3﹣10x2+20x
B．5x3﹣11x2+20x
C．6x3﹣9x2+20x
D．5x3﹣10x2+20x
Can you give ________ a call? [ ]
A. they
B. their
C. them
D. theirs
[ ]