含煤沉积物中常含（）结核。
参考答案：菱铁矿
Think twice before you make a decision on this matter. It will make ______ to your life.
A．no difference
B．a difference
C．little difference
D．difference
有一个数十位和百分位上都是6，个位和十分位上都是0，这个数字写作______，把他精确到十分位约等于______．
