Ethan took the rubber cap off and made a tiny hole in it.

伊桑取下了橡皮帽，在上面扎了个小孔。

Last of all, he put the rubber cap on the little bottle of milk.

最后他又把小奶瓶装上了橡皮帽。

Researchers discovered this by outfitting elephant seals with brain-monitoring rubber caps, but we'll get back to that.

研究人员通过给海象配备大脑监控橡皮帽发现了这一点，我们稍后会说到这一点。