OG详解-OG2 数学1 Q12

Choice D is correct. It’s given that the equation h = -4.9t²+7t +9 represents this situation, where h is the height, in meters, of the object t seconds after it is kicked. It follows that the height, in meters, from which the object was kicked is the value of h when t =0. Substituting 0 for t in the equation h = -4.9t²+7t +9 yields  h = -4.9 (0) 2+7(0) 9, or h =9. Therefore, the object was kicked from a height of 9 meters.
Choice A is incorrect and may result from conceptual or calculation errors. 
Choice B is incorrect and may result from conceptual or calculation errors. 
Choice C is incorrect and may result from conceptual or calculation errors.