Seeds in cone-bearing plants will begin to grown when
a-when they leave the parent plant
b-when they become fertilized
c-as soon as they hit the ground
d-conditions are favorable

Seeds in cone bearing plants will begin to grow when conditions are favoruable. The correct option is D. The cone bearing seeds are usually conifers which are the richest group of gymnosperm. A seed is a mature ovule which contains the fertilized egg. The seed contains the plant embryo, the sporophyte and its own food reserves. The embryo is protected and nourished until environmental conditions are right for germination. 

The infrared (ir) and the ultraviolet(uv) represent the two extremities of the visible spectrum (400-700nm). while ir represents electromagnetic radiation with wavelengths longer than those of visible light, uv represents wavelengths shorter than visible light