— Do you think he is naughty enough?

— I'm afraid he's ____ than naughty. [ ]

A. more clever

B. clever

C. much clever

D. much more clever

碳二加氢反应器开车前，氢气调节阀前闸阀要全关，是防止调节阀内漏，致使大量氢气漏入反应器造成飞温。