Read the following comprehension passage carefully and then answer the question by choosing the best option out of the four alternatives. There is a time in every man's education when he arrives at the conviction that envy is ignorance; that imitation is suicide; that he must take himself, for better or for worse, as his portion; that though the wide universe is full of good, no kernel of nourishing corn can come to him but through his own toil bestowed on that plot of ground which is given to him to till. The power which resides in him is new in nature, and none but he knows what that is which he can do, nor does he truly know it until he has tried. It is not without meaning that one face, one character, or one fact makes a deep impression on him and another does not. This sculpture in the memory is not without pre established harmony. The eye was placed where one ray should fall, that it might testify of that particular ray. We but half express ourselves, and are ashamed of that divine idea which each of us represents. It may be safely trusted as proportionate and of good issues if it is faithfully imparted, but God will not have his work made manifest by cowards. A man is relieved and gay when he has put his heart into his work and has done his best; but what he has said or done otherwise shall give him no peace. It is a deliverance which does not really deliver. In the attempt his genius deserts him; no muse befriends him; no invention, no hope appears. According to the passage, what is that which only the person himself truly knows and must act in order to discover fully?

Introduction / Context:
This question focuses on a key idea in the passage: the unique inner power that each individual possesses. The author emphasises that this power is "new in nature" and that no one except the person himself truly knows what he can do until he actually attempts to act. The question asks you to identify what exactly is known only to the person and must be acted upon in order to be fully discovered.

Given Data / Assumptions:

• The passage states: "The power which resides in him is new in nature, and none but he knows what that is which he can do, nor does he know until he has tried."
• The options mention untapped potential, destiny, the power residing in him, and the joy of success.
• The author connects knowledge of this inner power with actual effort and experience.
• We assume the question is asking for the phrase that matches the wording and idea of the passage most precisely.

Concept / Approach:
The author is stressing self knowledge that comes from action. He is not talking about a fixed destiny mapped out in advance, nor simply the emotional joy of success. Instead, he highlights a unique "power which resides" in each person. Only that person can discover the true extent and nature of this power by trying, by working on his own "plot of ground". Therefore, the correct answer must echo that specific phrase rather than paraphrasing it in a way that changes the focus.

Step-by-Step Solution:
Step 1: Identify the exact sentence in the passage that directly answers the question.Step 2: Note that it says, "The power which resides in him is new in nature, and none but he knows what that is which he can do."Step 3: Observe the condition that he himself does not fully know this power until he has tried, which connects knowledge with action.Step 4: Compare this with option C, "The power which resides in him." This is the precise phrase used in the passage.Step 5: Check that the other options either change the idea too broadly or introduce concepts (like destiny or success joy) that are not the central focus of that sentence.

Verification / Alternative check:
Option A, "His untapped potential", is conceptually similar but more general and does not capture the author's exact wording. Option B, "His destiny that lies in the future", suggests a fixed future path rather than a power discovered by personal effort. Option D, "The joy of achieving success", refers to a feeling that comes after accomplishment, not to the inner capacity itself. Only option C directly reflects the passage's language and meaning: a unique power residing in the person, discovered through action.

Why Other Options Are Wrong:
Option A may tempt students because "untapped potential" sounds like inner power, but the passage specifically emphasises "the power which resides in him", not just potential in a vague sense. Option B incorrectly shifts focus to fate or destiny, which the passage does not mention. Option D talks about "the joy of achieving success", which is an emotional result, not the inner power the author wants us to recognise and trust. Therefore, none of these alternatives matches the author's description as accurately as option C.

Common Pitfalls:
One common mistake is to choose an answer that captures the general idea but ignores the precise wording and emphasis of the passage. Exam questions often reward those who pay attention to the exact sentence that answers the question. Another pitfall is to be attracted by positive sounding words like "destiny" or "joy", which may feel inspiring but are not actually what the author is emphasising. Careful reading and matching of key phrases prevent these errors.

Final Answer:
The thing that only the person truly knows and must act in order to discover fully is the power which resides in him.