A:serious, seriou
B:seriously, seriously
C:seriously, seriou
D:serious, seriously
杉树是一种用材林木,为了使杉树长得又快又高,可采取的措施是( )
在平面直角坐标系中,若P,Q满足条件:(1)P,Q都在函数f(x)的图象上;(2)P,Q两点关于直线y=x对称,则称点对{P,Q}是函数f(x)的一对“可交换点对”.({P,Q}与{Q,P}看作同一“可交换点”.试问函数fx=x+3x+2x≤0log2xx>0的“可交换点对有( )