急性肺栓塞的实验室检查有（）

A.X线胸片可见肺实质病变，肺动脉高压

B.血气示动脉氧分压（PaO₂）＜10.7kPa（80mmHg）

C.心电图表现为电轴右偏型

D.超声心动图示右心室扩大

E.转氨酶增高

Which of the following is least likely to be considered a feature that is common to both monopolistic competition and perfect competition（）

A. Extensive advertising to differentiate products.

B. Zero economic profits in the long run.

C. Output where marginal revenue equals marginal cost.