An 18 month-old child is hypotonic and cannot fully extend the neck and trunk against gravity. Which position would be MOST EFFECTIVE to place the child in to facilitate antigravity movement and promote hand usage?

a. Fully upright in a standing frame
b. Prone on a 45 degree wedge positioned on the floor
c. Seated upright on a large therapy ball
d. Straddle-sit position on a bolster