Write and read. It can be whatever, just write. Just like anything, practice makes perfect. :)
The sentence is interrogative (B), as it is a question.
Hope this helped :)
It is answer C. They didn't understand the test and probably didn't know what they got wrong and couldn't study.
The answer is definitively "D". All the others do not use the possessive personal pronouns correctly.
I'd say C, "The acrylic pods are created in many sizes, including big, small, and medium, as well as other sizes needed by the scientists; they are connected to the seafloor by chains and float some distance below the surface, so the plants are not destroyed by storms."