单项选择题

已知y=ln(x+
),则下列正确的是( )。

A.dy=<br /><img src="https://imgtest.ppkao.com/ExamPaperRes/2018/12/13/cc59f8ce8a844edbb170300da8ddc7e5/a2ae483b-8c26-4e42-af0e-670cbb3f4c4d.jpg">
B.y′=<br /><img src="https://imgtest.ppkao.com/ExamPaperRes/2018/12/13/cc59f8ce8a844edbb170300da8ddc7e5/6f942745-79fb-4161-b8b4-7f5a3198d17a.jpg">
C.dy=<br /><img src="https://imgtest.ppkao.com/ExamPaperRes/2018/12/13/cc59f8ce8a844edbb170300da8ddc7e5/b499705d-b6c3-499f-9c9d-26b8d1ea9ef1.jpg">
D.y′=<br /><img src="https://imgtest.ppkao.com/ExamPaperRes/2018/12/13/cc59f8ce8a844edbb170300da8ddc7e5/825cdc32-71cb-4065-b3e6-87814fef59c9.jpg">