Let $C^{\infty }\left ( 0,1 \right )$ stand for the set of all real-valued functions on $\left ( 0,1 \right )$ that have derivatives of all orders. Then the map $C^{\infty }\left ( 0,1 \right )\rightarrow C^{\infty }\left ( 0,1 \right )$ given by
$$f \mapsto f+\frac{df}{dx}$$
is
- injective but not surjective
- surjective but not injective
- neither injective nor surjective
- both injective and surjective