下面哪种是kennedy第二类牙列缺损（）
A.A
B.B
C.C
D.D
E.E
参考答案：D
除0外，自然数不是质数就是合数。[ ]
It is__________ his advice on how ___________English well_________ you a lot of trouble. [ ]
A. because; to learn; that will avoid
B. taking; to learn; that will save
C. because of; learning; which will waste
D. for;learning;that will make
