A:CH4和C2H2
B:CH4和C2H4
C:C2H6和C2H2
D:C2H4和C2H2
脊椎动物的共同特点是身体内都有由____组成的____.
若函数fx=sin3x+φ,满足fa+x=fa-x,则fa+π6的值为( )