题目

阅读理解 Technology offers conveniences such as opening the garage door from your car or changing the television station without touching the TV. Now one American company is offering its employees a new convenience: a microchip implanted in their hands. Employees who have these chips can do all kinds of things just by waving their hands.Three Square Market is offering to implant microchips in all of their employees for free.Each chip costs $300 and Three Square Market will pay for the chip.Employees can volunteer to have the chips implanted in their hands.About 50 out of 80 employees have 下面是小青同学对部分化学知识的认识，其中不正确的是（      ） A．用托盘天平称取5．6g氯化钠          B．给试管中物质加热要先预热 C．水壶的水垢可以用食醋浸泡除去        D．人体所需的元素应尽量从保健品中摄取