下列常用词语的字音完全正确的一项是

A．针砭biān　纰bǐ缪miù 翩piān跹xiān

B．粗糙cāo 　回溯sù 　　内疚jiù

C．绦虫tāo 　砧板zhēn　恸哭tòng

D．粗犷guǎng 毁谤huǐ 　讷言nè

Which of the following statements regarding a monopolist is most accurate （）

A. A monopolist will maximize the average profit per unit sold.

B. If a firm has a monopoly, it will always be able to earn economic profits.

C. A monopolist, like any other profit-maximizing firm, will sell at the output level where marginal revenue equals marginal cost.