Answer:
Adjective Clause: The book I’m reading.
Step-by-step explanation:
The book I’m reading is a adjective clause because the sentence completes the meaning. For example, “Let me show you” is one complete sentence. But the clause “The book I’m reading” clearly explains and completes the sentence. It also defines the reader that the Subject was reading a book and would show the book to the second person. Hence by combining the clause “Let me show you” and the clause “the book I’m reading” completes the sentence. Hence, the option “The book I’m reading” is the adjective clause.