简述计算机的性能指标
参考答案：
基本字长，存储容量，运算速度，系统可靠性，外部设备和软件配置。
How can you expect him to make any progress ________ you never give him a chance to have a try?
A．when
B．unless
C．even though
D．until
麻黄发汗解表宜生用，止咳平喘宜灸用。
