The correct answer is bridges.
The answer is A because the subject is responding to something that is going on outside of it, if that makes any sense :)
Hope this helps! Have a great day!
Answer:proton
For our purposes at this point in the text, we can define an acid. as a substance with at least one hydrogen atom that can dissociate to form an anion and an H + ion (a proton) in aqueous solution, thereby forming an acidic solution.
Explanation: hope it helps!
