voluntary obligatory right

例句：

1. 1.They decided to volunteer for the community service project.
   他们决定为社区服务项目做志愿者。
2. 2.The voluntary donation is tax deductible.
   这个自愿捐赠是可抵扣税款的。
3. 3. The company has a policy of voluntary retirement at age 65.
   该公司有一个政策，员工可以在65岁后自愿退休。