Adaptive radiation is illustrated in

It's actually A (modified insect mouthparts). I got the explanation below online.
ENT 425 - General Entomology
Mouthparts

The ancestors of present-day insects were probably worm-like arthropods with a simple mouth opening near the front of a bilaterally symmetrical body. Over many eons of time, tissues and appendages near the mouth opening came to be adapted for gathering and manipulating bits of solid food. As insects evolved, they became more complex, expanded in range, and adapted to new food resources. The structure and function of their mouthparts changed right along with their evolving diet and life style. This is an excellent example of adaptive radiation (an evolutionary process in which two or more populations, exposed to different selective pressures, diverge from a common ancestor). Examples of adaptive radiation can be found just about everywhere in the insect world (think about variability in legs, wings, and antennae, for example).