You can use a scanner to quickly copy documents or pictures onto paper.

多项选择题关于血小板输注无效的可能原因，正确的是（ ） A、发热 B、感染 C、 产生HLA抗体 D、产生HPA抗体

单项选择题What is the time preference? A、People prefer the present consumption. B、People prefer the future consumption. C、Compared with the future consumption people prefer the present consumption. D、Compared with the present consumption people prefer the future consumption.