Answer:
The structures are attached in file.
Hydrogen bonding and intermolecular forces is the reason for ranks allotted.
Explanation:
In determining Lewis structure, we calculate the overall number of valence electrons available for bonding. Making carbon (the least electronegative atom) the central atom in the structure, we allocate valence electrons until each atom has achieved stability.
In order of decreasing affinity to water molecules:
This is due to the fact that the 
will accept protons more readily than the bicarbonate ion, 
. Carbonic acid, 
will not accept any more protons, hence it is the least attractive to water molecule, even though soluble.
Answer:
C. It blocked out sunlight
Explanation:
The asteroid impact 65 million years ago was devastating for lot of the animals and plants, resulting in a mass extinction, most noticeably of the dinosaurs. The impact itself killed a lot of flora and fauna, but it was the effect afterward that was crucial. From this impact, there was so much debris propelled into the atmosphere that the sunlight got blocked. Once this happened, most of the plants died out as they were not able to perform photosynthesis. Because the plants were dying out, the herbivores were left without food, so soon they followed, and because the herbivores died out, the predators died out to because they were left without food. The winners turned out to be the small and not specialized plants and animals.
