Which of the following is an irrational number?

Calculations:

\(\sqrt{1 \cdot 44} \) = 1.2 (not an irrational number)

\(−\sqrt{0 \cdot 64}\) =  -0.8 ( rational number not an irrational number)

(√5 + 1) (√5 − 1) = 5 - 1 = 4 (By a² - b² = (a - b)(a + b) (rational number it is)

√7 − 8 = Irrational number 

Hence, The Correct Answer is option 3.