form表单提交参数遇到的问题

Question

提交参数时不止哪里多了一个string`<div class="row loan-padding loan-coupon">                                <select class="form-control fcs-select border-white" name="placementId" ng-model="invest.coupon" ng-options="coupon.id as coupon.label for coupon in invest.coupons">                                     <option>使用奖券</option>                                 </select>                             </div>`