Triple x syndrome, or trisomy x, occurs when a female has an extra x chromosome in each of her cells. this results when the mother's reproductive cells divide improperly, and two x chromosome are moved into one gamete. when that gamete is fertilized and the father's dna and x chromosome are combined with the mother's, that gives the cell three x chromosomes instead of two. triple x syndrome occurs because
a) crossing over
b) nondisjunctions
c) point mutations
d) deletions

B) Nondisjunction.

Explanation: Syndromes such as triple X syndrome, Turner's syndrome, Down syndrome, and Klinefelter's syndrome occur because of nondisjunction, or the improper separation of the chromosomes during division. In each of these cases, an extra chromosome (X chromosome for triple X, chromosome 21 for Down syndrome, etc.) causes symptoms in the offspring. In some syndromes, such as triple X syndrome, the symptoms are often not very noticeable.

the answer is b)3/8x+1