I know the answer it is...
The formula for aluminum fluoride is 
That means that there is 1 Aluminum and 3 fluorde ions in 1 molecule. The 3 does not effect the Aluminum at all.
The Answer is A
It looks like something to screw onto something and manage the flow of... I'd say... knob for a screw
All wavelengths/colours that are visible make up white light. From violet (between 380 nm and 450 nm) to red (between 400 nm and 700 nm).