<prompt> True for a 2yrs old boy isWeight four times that of bih weightRides bicycleClimbs up and down the stairs with alternating stepsOssification center for radius head appears  <response>: At 2yrs weight becomes 4 times that of bih at bih 3kgs, at 2yrs 12kgs A child is able to ride a bicycle by the age of 3yrs A child is able to climb up and down the stairs at 4yrs Ossification center for radius head appears at 3-4 yrs of age. Ref: Ghai ,9th edition, chapter 2 3. 