So to make choice a correct, the semicolon should be a comma. That should help with choices B and C also. Answer C is correct, because there are only 2 ways you can use 'however': at the beginning of a sentence followed by a comma or. :)
"although the sun was shining, it wasn't that warm" is the correct answer because it contains a main clause (it wasn't that warm) and a prepositional phrase (although the sun was shining,). Hope this helps :)
Fillers are words that are part of spoken language but do not contain any meanings. These are usually referred to as unnecessary pauses in speaking such as using the words uhm, uh or er. The best way to avoid using filler words is to plan carefully so that you don't lose your train of thought.
This all depends on what you are going to be writing or speaking about. If you told me, I would be glad to help.
