A:a; substitute
B:a; replace
C:/; substitute
D:/; replace
— What do they do on Sunday afternoon?
—They take a d____ class in the gym.
热带和亚热带绿洲农业的代表植物是( )
定义在R上的函数fx满足fx=-f2-x,且当x<1时fx递增, 若x1+x2>2,(x1-1)(x2-1)<0则fx1+fx2的值是 ( )