下列中国古代科技著作中，成书于汉代的是（）
A.《本草纲目》
B.《齐民要术》
C.《九章算术》
D.《石氏星表》
参考答案：C
希望小学今年毕业的学生人数比去年毕业的多10%，今年毕业生人数比去年多了20人，去年有______名毕业生．
Jack is ______go to school,so his mother has to stay at home to look after him.
A．young enough to
B．old enough to
C．too young to
D．very old to
