Explanation:

- Average without new student: The average marks of the original three students is \( x \), so their total marks is \( 3x \).

- Average with new student: The new student increases the average by 2, making it \( x + 2 \). Since there are now four students, their total marks is \( 4(x + 2) \).

- Equation setup: Equating the two total marks expressions, we have:

$$ 3x + \text{(marks of new student)} = 4(x + 2) $$

- Simplify equation:

$$ 3x + \text{(marks of new student)} = 4x + 8 $$

$$ \text{Marks of new student} = 4x + 8 - 3x $$

$$ \text{Marks of new student} = x + 8 $$

- Correct Option: The marks secured by the new student is \( x + 8 \).

X + 8 is the correct answer.