C.                                    D.

36. 设 z=ln(x+e ), 则 (         )

A.                                                      B.

C.                                                   D.

37. 设 z=sin(x²-y²) 则 (         )

A.-sin(x²-y²)                                                     B.sin(x²-y²)

C.-4x²sin(x²-y²)                                              D.-4x²sin(x²-y²)+2cos(x²-y²)

38. 设 z= 则 dz （       )

A.                                           B.

C.                              D.