我们有必要参加开幕式.用英语怎么说？

我们有必要参加开幕式.

We were obligated to attend the opening ceremony.

we

pron. 我们，咱们，笔者，本人，朕，人们；

例句
...expensive make-up that we saw being advertised by a beautiful model...
我们所见的由一位漂亮模特代言的昂贵化妆品

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

obligated

adj. 有义务的，必须的，有责任的；v. 使负有责任或义务（ obligate的过去式和过去分词 ）；

例句
Under a separation agreement, he was obligated to pay his ex-wife £50,000 a year for life.
根据分居协议，他必须每年向前妻支付5万英镑。

to

prep. 向，朝着，到，关于，属于；adv. 朝一个方向的，到某种状态，关闭；

例句
I suggest you leave it to an expert...
我建议你把它留给专家来解决。

attend

vi. 出席，致力于，献身于，侍候，照顾，关注；vt. 出席，参加，[常用被动语态]（作为结果、情况）伴随，照顾，陪伴；

例句
The staff will helpfully attend to your needs...
工作人员会帮忙满足您的需求。

the

art. 指已提到的人（物），指说话人与听者已知的人（物），用于独一无二的事物前，与形容词最高级和序数词连用；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

opening

n. 开幕，开始，空缺的职位，[商]开盘，交易开始时间，（职位的）空缺；adj. 首次的，开始的；v. （打）开( open的现在分词)，开始，睁开，启动；

例句
The hallowed portals of academe were slowly and grudgingly opening to women.
大学神圣的大门缓慢又勉强地向女性敞开。

ceremony

n. 典礼，仪式，礼仪，礼节，虚礼，客气；

例句
The appointed hour of the ceremony was drawing nearer.
既定的典礼时间就快到了。