Answer: ≈0.71
Step-by-step explanation: The real decimal would be 0.70710678118655. Yes, I know it is a big number. So, after doing some calculations, I got 0.5, remember we need to find the square root of 0.5. So, after finding that, I got 0.70710678118655. Which, your answer wants it to be rounded, so it would be D: ≈0.71