In the sentence given in question, The word "<u>clouds</u>" is simple subject and the word "<u>obscured</u>" is simple predicate.
What is subject in grammar?
Technically, According to a tradition dating back to Aristotle (and connected with phrase structure grammars), the subject is one of a clause's two basic components, the other being the predicate, which expresses something about the subject. The subject is the main overt argument of the predicate, according to a tradition connected to dependency grammars and predicate logic. According to this view, all languages that support arguments have subjects, albeit it is impossible to define this universally across all languages. Even in languages like English, the semantic predicand and the subject are not always perfectly matched because a predicate could be based on an argument in another clause (see raising).
In this sentence which is given in the question, "Clouds of dust around the van obscured our vision.", "<u>obscured</u>" is the verb so it is working as a simple predicate. and the word "<u>clouds</u>" is the noun or pronoun so it is working as a simple subject.
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