This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
Barr body is absent is females having - 
Select and explain. 
A. 46 XX genome, B. 45 XO genome, C. 47 XXX, D. All of the above
B: 45 XO genome
Answer: B: 45 XO genome 
Explanation: Barr body 

Discovered by Murray Ban
Inactive X-chromosome
Usually in female, One X-chromosomes is always inactive and detected as Barr body.
Normal 46 XX → One barr body seen
Super female 47 XXX → Two barr body seen
Klinefelter 47 XXY(males) → Single barr body
Turner 45 XD → Barr body absent
Barr body is seen in nucleus of neutrophils.

Barr body: 

Sex chromative mass seen within nuclei of normal female somatic cell.
Acc. to Lyon hypothesis, one of two x-chromosome in each somatic cell is genetically inactive and repersent barr-body.
Klinefilter syndrome (XXY) → One inactive X-chromosome ban body.
If XXXY = 2 Ban body

XO = 0 Ban body
XY = 0 Ban body
XX = 1 Ban body