在可摘局部义齿的设计中，为防止义齿下沉，刺激牙龈组织，不宜单独使用

A．间隙卡环
B．环形卡环
C．三臂卡环
D．对半卡环
E．双臂卡环

An analyst does research about price multiples. For a given company, price to earnings ratios are generally more stable from period to period than:

A. price to sales ratios but not price to cash flow ratios.
B. price to cash flow ratios but not price to sale ratios.
C. neither price to sales ratios nor price to cash flow ratios.