下列岩石经变质作用形成片麻岩的是[ ]
A．花岗岩
B．砂岩
C．石灰岩
D．页岩
答案：A
The square box has a door, there are some buttons.
A．beside it
B．beside which
C．beside that
D．beside what
生活饮用水卫生标准中一般化学指标有多少项？其中对水的pH值和总硬度有何要求？
