▲extend 指时间或空间的延长，也可指影响和使用范围等的扩大。在此句中它指时间处长。用于此句符合句意：

With the art show extended for another week, it was possible formore fans to visit it. 艺术展延长了一周，这让更的爱好者有机会参观。

又如：

The hot weather extended into October. 热天气一直持续到 10月。

Management have agreed to extend the deadline. 管理层已同意延长最后期限。

The new law extends this ban beyond 2050. 新的法律将这条禁令延长至2050年。

This deadline will be extended only in exceptional circumstances. 只有在特殊情况下才延长最后期限。

▲expend 的意思是“花费”，指花费时间、金钱、精力、能量等，是 spend 的文语用词。如：

Don’t expend all your energy on such a useless job. 不要把精力消耗在这种无用的工作上。

Children expend a lot of energy and may need more high-energy foodthan adults. 孩子们消耗很多能量，可能比成年人需要更多高能量的食物。

I think it is safe to say that very few students expend the effortto do quality work in school. 我认为可以肯定地说学校里很少有学生肯为学好功课下功夫。

▲spread 指一直延伸、蔓延，侧重遍及。如：

The news has spread through the world. 那消息传遍了全世界。

By dusk the news had spread through the city. 到黄昏时消息已传遍全城。

If this disease spreads in the country, the doctors fear that there’llbe higher mortality. 医生担心这种疾病一旦在全国流行开来，死亡率会更高。