一、二年草本露地花卉皆为（）繁殖。
A.播种
B.嫁接
C.压条
D.扦插
参考答案：A
John thinks it won’t be long_________he is ready for his new job.
A．when
B．after
C．before
D．since
层次模型和网状模型统称为______模型。
