$($a$)$ Sentences $($S$)$ are recursive categories, and it can contain a subordinate clause in the form of that S $($ S stands for a sentence$).($i$)$ Explain what we mean by recursive category. $($ii$)$ Provide another type of example $($different from that S type$)$ of recursion within a sentence. $($iii$)$ Provide evidence that noun phrases and prepositional phrases are recursive categories as well. $($b$)$ Out of syntactic structure and recursion, which is the most basic property of human language? Ex$-$ plain. In answering this question, consider whether syntactic structure can exist without recursion or the other way around.