23.  The efficiency E of a screw jack is given by E = $\frac{\tan \theta }{\tan (\theta +\varphi )}where \theta is variable and \varphi is some$ constant angle lying in $\left(0,\frac{\mathrm{\pi }}{2}\right)$.  The maximum efficiency is given by
$A) \frac{1-\cos \varphi }{1+\cos \varphi } B) \frac{1-\sin \varphi }{1+ \sin \varphi } C) \frac{\cos \varphi }{3(1+\sin \varphi )} D) \frac{\cos \varphi }{1+ \cos \varphi }$