What is the subordinate clause of the following sentence? is it a noun, adjective, or adverb clause?: I recommend that you take the red boat, it is the fastest.
I recommend that you take the red boat, it is the fastest.
that you take the red boat=== NOUN Clause.
Well, let's question the verb(recommend)
--what do I recommend?
ans. (you take the red boat) .
So, (that you take the red boat) is the object of the verb 'recommend'.
As it is an object, it must be a NOUN clause.
Let's have an another example for better understanding:
I know that you are good.
Q. What do I know?
A. (you are good)
that you are good === object of know verb === NOUN clause.
Hope it must be cleared to you.