复选框必需属性

Question

您好我已经使用此代码作为我的复选框，我想要点击任何按钮（链接）之前，您应该先单击复选框。什么似乎是问题？或者我在代码中缺少什么

//check box EULA
sb.Append("<br/><input type='checkbox' name='eula' required='true' /> By clicking Accept, you confirm that you are ready to proceed with this purchase, have read the terms and conditions, that you understand them, and that you agree to be bound by them. Please expect an invoice soon after.<br>");

// this contains message description w/ name
sb.Append("<table border='0' cellpadding='0' cellspacing='0' width='100%;'><tr><td width='260' valign='top'> <br><br></td><td style='font-size: 0; line-height: 0;' width='20'> &nbsp;</td><td width='260' valign='top'><div style='float:right;'><br>");

//buttons
string accept_link = Url.Action("AcceptQuotation", "ServiceRequest", new { id = serviceRequest.EmailHash }, Request.Url.Scheme);
string decline_link = Url.Action("DeclineQuotation", "ServiceRequest", new { id = serviceRequest.EmailHash }, Request.Url.Scheme);
string comment_link = Url.Action("CommentQuotation", "ServiceRequest", new { id = serviceRequest.EmailHash }, Request.Url.Scheme);

sb.Append("<a href='" + accept_link + "' style='cursor:pointer; padding:1vh; padding-left:3vh; padding-right:3vh; border-style:none; background-color:#7AC142; color:white; text-decoration:none; margin-right:10px;'>Accept</a>");
sb.Append("<a href='" + decline_link + "' style='cursor:pointer; padding:1vh; padding-left:3vh; padding-right:3vh; border-style:none; background-color:#EE6363; color:white; text-decoration:none; margin-right:10px;'>Decline</a>");
sb.Append("<a href='" + comment_link + "' style='cursor:pointer; padding:1vh; padding-left:3vh; padding-right:3vh; border-style:none; background-color:#4badff; color:white; text-decoration:none;'>Comment</a>");

sb.Append("</div></td></tr></table></td></tr></table></td></tr><tr><td><table border = '0' cellpadding = '0' cellspacing = '0' width = '100%' ><tr><td colspan='4' bgcolor='#F3AD61' style='padding:3vh; text-align:center; color:white;'> Connect with Full Suite</td></tr><tr bgcolor='#F3AD61'><td style='padding-left:90px; padding-right:20px;'> <a target='_blank' href='https://www.facebook.com/fullsuite/' style='text-decoration:none; float:right;'> <img src='http://full-suite.azurewebsites.net/Content/Images/Email/fb.png' width='40' /> </a></td><td style='padding-left:0px;'> <a target='_blank' href='https://www.instagram.com/fullsuite/' style='text-decoration:none;'> <img src='http://full-suite.azurewebsites.net/Content/Images/Email/ig.png' width='40' /> </a></td><td style='padding-left:0px;'> <a target='_blank' href='https://www.linkedin.com/company/fullsuite' style='text-decoration:none;'> <img src='http://full-suite.azurewebsites.net/Content/Images/Email/li.png' width='40' /> </a></td><td style='padding-right:100px;'> <a target='_blank' href='https://twitter.com/fullsuite?lang=en' style='text-decoration:none;'> <img src='http://full-suite.azurewebsites.net/Content/Images/Email/tw.png' width='40' /> </a></td></tr ><tr><td colspan='4' bgcolor='#F3AD61' height='25'></td></tr></table ></td></tr></table></table></body></html>");