The GATE Grind

GATE 2024 MA – Question 38

Real Analysis · Measure and Integration · 2 marks · Multiple choice

Which condition suffices for f:[0,1]→ℝ to be Lebesgue measurable?

  1. |f| is Lebesgue measurable.
  2. Continuous g,h satisfy g≤f≤h.
  3. f is continuous almost everywhere.
  4. Every level set {x:f(x)=c} is measurable.

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (C) f is continuous almost everywhere.

Explanation

A function continuous except on a null set is measurable: its restriction to the continuity set is Borel measurable, and arbitrary changes on a null set preserve Lebesgue measurability. Thus **C**. A sign choice on a nonmeasurable set can have |f|≡1 and be bounded by continuous constants, refuting A,B. Measurability of individual level sets alone does not ensure that inverse images of intervals are measurable.

More Measure and Integration questions

All Measure and Integration questions →