注意，句中的 who want to 是修飾anyone 的定語(yǔ)從句，所以原句的基本結(jié)構(gòu)是：At this booth, anyone could paint a square. 　　

另外注意，在這類表達(dá)的定語(yǔ)從句中，to 后面通常有個(gè)“不言而喻”的動(dòng)詞被省略了，比如上面這個(gè)句子，可視為省略了paint，即原句可理解為：At this booth, anyone who want to paint could paint a square. 　　

類似含有這類  could to 的例句如：　　

They did what they could to console her. 他們盡量安慰她。　　

We did all we could to make the room beautiful. 我們盡可能把房間布置得漂亮些。　　

下面的 can to 也屬同樣情形：　　

We will do what we can to help you. 我們?cè)敢獗M力幫助你。　　

Please do what you can to expedite the building work. 請(qǐng)盡量加快建筑工作。　　

Such people will do anything they can to make mischief. 這種人會(huì)不擇手段地搞破壞。