If a + b = 1, c + d = 1 and a b =d , then the value of c2 d2 isc

• A. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>a</center></td></tr><tr><td style="text-align: center;">b</td></tr></table>
• B. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>b</center></td></tr><tr><td style="text-align: center;">a</td></tr></table>
• C. 1
• D. 1