我觉得是：two bows and arrows

我的分析：指一个人用的“弓箭”，可以是 a bow and arrows，因为一把弓会配备多支箭；但如果是指两个人或更多的人，则用 bows and arrows，因为每人一把弓，同时要配备很多箭。如：

The two brothers used bows and arrows for hunting. 这两兄弟用弓箭打猎。

Some of the raiders were armed with bows and arrows. 有些偷袭者配备了弓箭。

Warriors armed with bows and arrows and spears have invaded their villages. 佩有弓箭和长矛的武士们已入侵了他们的村庄。

类似例句如：

He had on a raincoat and boots. 他穿着雨衣和靴子。

They had on raincoats and boots. 他们穿着雨衣和靴子。

He disguised himself in a wig and glasses. 他戴上假发和眼镜来伪装自己。

They disguised themselves in wigs and glasses. 他们戴上假发和眼镜来伪装自己。

He equipped himself with a hammer and nails. 他随身带了把锤子和一些钉子。

They equipped themselves with hammers and nails. 他们随身带了锤子和钉子。