汤纳特尔（R.J.Donatell）将健康分为（）个级别，每个级别又有水平的高低。
参考答案：三
Now many people move into cities in order to have their children __________.
A．better educate
B．receive well education
C．better educated
D．accept better education
热凝塑料填塞的最佳时机是（）。
A.橡胶期
B.稀糊期
C.面团期
D.黏丝前期
E.黏丝后期
