在关系式y=3x+4中,当自变量x=7时,因变量y的值是( )
A:1
B:7
C:25
D:31
—You'd better go to see a dentist.
— Who's that young man on the poster?— Justin Bieber, excellent singer.
成语“罄竹难书”出自《旧唐书•李密传》:“罄南山之竹,书罪未穷;决东海之波,流恶难尽”这是李密为声讨哪一个人物而写的( )