Identify the clause of the highlighted part of the given sentence.
I am glad that you have liked it.

Correct option is B

The correct answer is (b) Adverb.
The highlighted clause “that you have liked it” explains the reason for being glad and modifies the adjective glad. Since it answers the question why, it functions as an adverb clause in the sentence.
• Grammatical rule involved (English):
A clause that modifies a verb, adjective, or another adverb by answering questions like why, when, how, or to what extent is called an adverb clause.
• व्याकरण नियम (Hindi):
जो clause verb, adjective या adverb के अर्थ को स्पष्ट करे और क्यों, कब, कैसे जैसे प्रश्नों का उत्तर दे, उसे Adverb Clause कहते हैं।
• Meanings / role of the other options:
• (a) Adjective Clause: Modifies a noun, which is not the case here.
• (c) Principal Clause: The main clause is I am glad.
• (d) Noun Clause: Does not act as subject or object here.
Thus, the correct option is (b).