A. Adaptations
A behavioral adaptation is a change affecting the way an organism naturally acts. This type of adaption could be caused by a change in the surrounding environment or the actions of another species. For example, predatory animals might start hunting in packs -- giving them an evolutionary advantage over solo hunters.
The answer is b. This can be remembered if you know that photosynthesis creates oxygen. Just remember that 'phytoplankton' starts with 'ph' just like 'photosynthesis', and you'll know that phytoplakton also create oxygen.
The most direct effect of severing the corpus callosum would be that the cerebral hemispheres could not directly communicate, since the corpus callosum is the set of nerve fibers that unites both cerebral hemispheres, this structure is located in the midline of the brain, situating itself in the interhemispheric fissure and being mostly hidden from external observation when it is partially obscured by the Cortex.
A scientific theory is a theory that explains the scientist's observations, whereas a scientific law is a repeated pattern in the world that we have not sought an explanation for.