a. all the function of the form 1 x x^2 ... are lineary independent (you can't have for example 1= a1*x^2+a2*x^3+... for any finite members of this group)
b striaght forward: let f,g be any functions and a real number then d(af+g)/dx=adf/dx+dg/dx
c.e^x is eigenvector (with eign value 1) actually e^ax is eigenvector (with the eignvalue a)