长江经济带能够实现东部沿海与中西部地区良性互动,是因为长江流域具有( )
已知f1(x)=sinx+cosx,记f2(x)=f1′(x),f3(x)=f2′(x)fn(x)=fn﹣1′(x)(n∈N*,n≥2),f1π4+f2π4+f3π4+f2013π4=( )
—Mum, can I have something _______?
—Oh, dear. You can only drink some water. There is _______ in the kitchen.