用300颗种子做发芽实验，有285颗发芽，这些种子的发芽率为______%．
285300×100%=95%；
答：发芽率是95%；
故答案为：95．
When she was three years old, she _____ sing several English songs. [ ]
A. may
B. must
C. can
D. could
什么是固定性制造费用成本差异的“双差异分析法”和“三差异分析法”？
