Which one of the following is the transfer function of an electrical low pass filter using R and C elements?

• A. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>RCS</center></td></tr><tr><td style="text-align: center;">(1 + RCS)</td></tr></table>
• B. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> 1</center></td></tr><tr><td style="text-align: center;">(1 + RCS)</td></tr></table>
• C. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> RC</center></td></tr><tr><td style="text-align: center;">(1 + RCS)</td></tr></table>
• D. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center> S</center></td></tr><tr><td style="text-align: center;">(1 + RCS)</td></tr></table>