Identify the type of subordinate clause in the following sentence.

The trouble was that he forgot where he put his keys.

noun.

adjective.

adverb.

The subordinate clause in the sentence "The trouble was that he forgot where he put his keys" is a noun clause.

A subordinate clause is a clause that is dependent on the main clause. It cannot stand alone. The subordinate clause in this sentence is: "The trouble was that". The main clause in this sentence is: "he forgot where he put his keys". From the above we can see that the main clause can stand on its own but the subordinate clause cannot stand on its own.