China's youths topped a list of calculating abilities ,  but ranked last on _____ imagination and 5th

from _____ bottom for creativity,  according to an education survey of 21 countries and regions.[      ]

A .  the ; the  

B.  an; the  

C.  /;/  

D.  /; the

浆细胞龈炎

A．牙龈增生常覆盖牙冠的2/3以上
B．牙龈 * * 红肿
C．牙龈线性红斑
D．牙龈鲜红肿大，松软脆弱，表面呈结节或分叶状
E．龈 * * 和边缘龈的坏死 下列疾病牙龈的特征病损是