()是指凡经试验鉴定,审定合格,确有推广价值的新育成品种的原始种子。
A、良种
B、原种
C、原原种
D、一代原种
参考答案:C
65.Is_necessary to tell his father everything?
A.it
B.that
C.what
D.He
图示结构,截面A处弯矩MA的数值为()
A.5kN·m
B.10kN·m
C.15kN·m
D.20kN·m