以下各个指令中正确的是（）。
A.MOV CS，1000
B.OUT DX，AX
C.MOV BL，BP
D.MOV AH，DX
参考答案：B
国家学制系统中学校教育的第一阶段是______。
A decorator bought a bolt of defective cloth that he judged to be usable, in which ease the cost would be $0.80 per usable yard. If it was later found that only of the bolt could be used, what was the actual cost per usable yard ？（）
A.$0.60
B.$0.90
C.$1.00
D.$1.20
E.$1.70
usable, in which ease the cost would be $0.80 per usable yard. If it was later found that only 
of the bolt could be used, what was the actual cost per usable yard ？（）