Tip: Superscript with ^ , subscript with _ Use $$to open 2. agentx5 and$$ to close and you can do this: H$$_3$$O$$^+$$ Your choice options are a bit hard to see what they are intended to be, so while the question itself is clear, the options are not. Additionally you can use \rightarrow to do this: $$\rightarrow$$ I know it's been 15 hours since you posted this but if you still need an answer @jude90 then please reply back with a formatted set of choices so those who will try to answer will know what's going on :-) Native LaTeX code is one of the great features of this website, helps so much when writing chemical formulas or math symbols.