Answer:
C. chains of alternating silicon and oxygen atoms with attached organic groups
Explanation:
It contains Silicone-Oxygen backbone as found in Silicone Dioxide (silica) but it also has organic groups attached to this backbone with Carbon-Silicone attachments. This whole arrangement of Silicone, Oxygen and Attached organic groups make up Silicones.
Well a solid and a liquid is completely different from a gas. For a gas you need to have an air tight seal in order for the gas to stay in, or a special type of container so the gas doesn't decompose the container. And a liquid or a solid it's self explanatory. With some liquids you need special containers to hold the liquid so it doesn't decompose the container it's in.
Because atoms can join together to form molecules, which in turn form most of the objects around us.
Unfortunately you did not specify the electronic configuration in the question, however since one of the answers must be a halogen, i took the liberty to attach an image with the configuration (both the simple numeric and spdf form) for all the halogen and all you have to do is match the electronic configuration you have in your question to the one in the table attached and you can then deduce the answer.
Hope this helps.