Final answer:
The subject of this question is faith, and the correct answer is a) Faith.
Step-by-step explanation:
According to Hebrews 11:6, the subject of the question is faith. This verse states that God rewards those who diligently seek Him. In the context of the Bible, diligently seeking God means having faith in Him and trusting in His promises. Therefore, the correct answer to the question is a) Faith.