Explanation:

Let's break down the sentence to find the correct sequence:

- A: "staircase by which"

- B: "the discipline is a"

- C: "on his/her goals in life"

- D: "the person achieves success"

- E: "it helps a person to focus"

Now, let's look at the options:

1. Option:1, ABECD

- Meaning: Incomplete and disjointed.

2. Option:2, DEBCA

- Meaning: Illogical order and confusing.

3. Option:3, CEABD

- Meaning: Parts are out of logical sequence.

4. Option:4, BADEC

- Sentence: "The discipline is a staircase by which the person achieves success. It helps a person to focus on his/her goals in life."

- This is a coherent and logical sentence structure.

5. Option:5, EABDC

- Meaning: Parts don’t fit logically.

The correct answer is Option 4 - BADEC.