Ans. is 'c' i.e., 6 cm/year "After 4 years, the child gains about 5 cm in height every year, until the age of 10 years" -- O.P. Ghai. "An average child gains approximately 7-8 cm in height between the age of 2-6 years and 6-7 cm in height between 6-12 years". -- Nelson Amongst given option, 6 cm/year is the best answer.