Because the ureter's submucosal section is small in youngsters, the anti-reflux mechanism is ineffective, leading to vesicoureteral reflux.
Urine flowing backward from the bladder to one or both ureters and occasionally the kidneys is known as vesicoureteral reflux (VUR). Infants and young children are most frequently affected by VUR. Most kids with VUR don't experience long-term issues.
Normally, urine travels from the kidneys through the ureters and bladder before exiting the body. When a person has VUR, some urine may reflux through one or both ureters and perhaps reach the kidneys.
VUR is often graded by doctors from 1 to 5. The severity of the ailment ranges from grade 1 (the mildest) to grade 5 (the most severe).
Consequently, the right response is B.
To learn more about ureter, refer:-
https://brainly.com/question/15012787
#SPJ4