All of the following are irrational except √1 √1.44 √2 √4

√4
This is rational, and the square root is 2

A rational number can be expressed as the ratio of two integers.  

Square root of 4 is 2, or 2/1, so sqrt(4) is rational.
sqrt(1.44) is 1.2 = 6/5 (rational)
sqrt(1) is 1 = 1/1 (rational)

That leaves sqrt(2).  sqrt(2) is approx. 1.414 , which repeats and is not rational.

sqrt(2) is the only non-rational expression of the four given.

I believe the question was "All of the following are rational except ... "

because here all of the given numbers are rational except for sqrt(2).