当测定硬度时，存在Al3+干扰，选择（）消除干扰。
A.控制溶液的pH值
B.络合掩蔽法
C.氧化还原掩蔽法
D.沉淀掩蔽法
参考答案：B
We have done half the work so far. _____, we’ll have finished it by December.
A．Unluckily
B．Fortunately
C．Hopefully
D．Thankfully
