单独一个which后面可以跟is，也可以跟are。

跟is时相当于which one；跟are时相当于which ones。例如：

【单数用法】

Which is more beautiful, the peony or the camellia? 牡丹花和山茶花，哪一种更美丽？

Which is the most interesting subject for you? 哪个科目对你来说最有趣？

But there are two pedals. Which one is the brake? 但是那儿有两个踏板。哪一个是刹车呢？

Which one is the longest river in China? 中国哪条河流最长？

【复数用法】

Which are the best headache tablets? 哪些药片治头痛最好？

Which are the last two states that join the union? 最后加入的两州是什么?

Rank them in order of priority: Which ones are most important to you? 按优先级的次序排列他们:哪些观众对您来说是最重要的?

Please look at the pictures on Page10, and discuss which ones are natural clones and which ones are man-made. 请看第10页的图片，并讨论哪些是自然克隆，哪些是人为的。

所以，你的看法是正确的。