强度等级为42.5的普通硅酸盐水泥，3天抗压强度指标值为（）。
A、15Mpa
B、16Mpa
C、17Mpa
D、121Mpa
参考答案：B
不等式4x-6≥7x-12的正整数解为（ ）。
--- How long has your mother ______ Beijing?
--- About two weeks. But she will come back tomorrow.
A．been to
B．been in
C．gone in
D．gone in
