用所给词的适当形式填空
已知函数fx=cos2x+φ满足fx≤f1对x∈R恒成立,则( )
一定温度下,某反应达到平衡,平衡常数K=c(CH3OH)c(CO)·c2(H2)。恒容时,温度升高,H2浓度增大。下列说法正确的是( )
Mark Twain ______ school and began to work at the age of twelve.