Identify the clause in the given sentence and mark the name of the clause as your answer. He didn't know why the engine wasn't working.

Noun Clause: A noun clause is used to name something when a single word isn't enough. They're always a dependent clause. They also acts as a subject of the sentence. Noun clause always gives the answer of "what". For eg: What Mohan wrote surprised her family. Adjective Clause: An adjective clause is a type of dependent clause that works to describe a noun in the sentence. Adjective clause gives the answer of "what kind of" For eg: People who are smart answer the question. Adverb Clause: An adverb clause is a type of dependent clause that functions as adverbs.Adverb clause answers How? Where? When? Why? For eg: When the clock strikes midnight he has to leave the town.A noun clause can also act as the object of the sentence when it answers what?In the given sentence, He didn't know after this you ask a question what? You will get the answer "why the engine wasn't working." So the correct answer is option 1 i.e. Noun clause.