(a-b)3·(a-b)5= ( ); (x+y)·(x+y)4=( )
(a-b)8;(x + y)5
Oil fires are best extinguished by().
A.cutting off the supply of oxygen
B.removing the fuel
C.cooling below the ignition temperature
D.spraying with water
()网球场地是草地场地。