有些语法书上说：what引导主语从句时的主谓一致主要看语境，此时若表语是复数，则主句谓语动词用复数；反之，若表语是单数，则主句谓语动词用单数。如：

What we need is money.

What we need are books.

但是，请看下面这句，来自2021年高考英语新全国卷I的语法填空题：

What is so breathtaking about the experience is the out-of-this-world scenes.

明明表语是复数 scenes 啊，为什么主句谓语动词用了单数？

附全文（加粗单词为填好的答案）：

Going to Mount Huangshan reminds me of the popular Beatles’ song “The Long and Winding Road”. What is so breathtaking about the experience is the out-of-this-world scenes. The rolling sea of clouds you see once you are at the top will remind you how tiny we humans are.

The hot spring at the foot of the mountain is something you must try after the climb. It will undoubtedly help you get refreshed! The amazing thing about the spring is that the colder the temperature gets, the hotter the spring! Strange, isn’t it? But that’s how nature is—always leaving us astonished.

What comes next is the endless series of steps. You can’t help wondering how hard it was for the people then to put all those rocks into place. Though it is the only unnatural thing on your way up the mountain, still it highlights the whole adventure and offers a place where you can sit down to rest your aching legs.

As the song goes, this long and winding road “will never disappear”, and it will always stick in the visitor’s memory. It sure does in mine. While you’re in China, Mount Huangshan is a must to visit!