侧根
参考答案：
主根生长达到一定长度，在一定部位上侧向地从内部生出许多支根。
递等式计算．
2400÷80-14×2
（720÷8+21）×3
400÷[300-（260-160）]．
"We will learn English words this year," the teacher said to the students.
A．one thousand three hundred and twenty-one
B．a thousand and three hundred twenty-one
C．one thousand three hundred twenty-one
D．a thousand three hundreds and twenty-one
