As for this problem, the most probable answer and the most likely answer for this one would be D. the effect of pesticides on organisms in the environment.
A toxicologist would only study about chemicals and their effect on organisms in the environment. Pesticides are chemicals made to combat organisms that aren't wanted particular parts of the environment such as crops and rice field. These pesticides don't just affect those organisms that are targeted, but even the users and other organisms that may have come in contact with pesticides.
Answer:
D. A silent variant near the 5' end of the TBX1 gene.
Explanation:
TBX1 gene is wild type human being. It gives instructions for making protein called T-box 1. It plays an important role in tissue formation and organs during embryonic development.
I would think that an unweathered rock would be jagged while a weathered rock would be smooth because of water/wind or what ever weathered it.
I believe the answer is littoral zones.
Sorry if I'm wrong, Hope this helps.
Wind turbines rely on wind, which will continue to be available.