下列等式中哪一个可以成立（）？<br>A:d<img src="/Image1/2e/2e2966124f2d142553b41d00a2231c93.jpg" />f（x）dx=f（x）<br>B:d<img src="/Image1/2e/2e2966124f2d142553b41d00a2231c93.jpg" />f（x）dx=f（x）dx<br>C:（d／dx）<img src="/Image1/2e/2e2966124f2d142553b41d00a2231c93.jpg" />f（x）dx=f（x）+c<br>D:（d／dx）<img src="/Image1/2e/2e2966124f2d142553b41d00a2231c93.jpg" />f（x）dx=f（x）dx