Women have two X chromosomes out of which one is active and the other is tightly folded or heterochromatic. Under the microscope, it appears as a Barr body. The number of Barr bodies in humans is one less than the total number of X-chromosomes. A female suffering from Turner syndrome has 45 chromosomes instead of 46 chromosomes and the karyotype is 44+X.
So, number of Barr bodies = Total no. of X chromosomes - 1 i.e. 1-1 = 0
So, the correct answer is A.