C. because stimuli is how your body responds to something, and in this case, someone's heart rate increases WHEN their blood oxygen drop. Do you see how it responds? ;-)
Hydrogen ion, or H-, creates water when combined with a hydroxide ion, OH+.
The 'formula' for water is H20, two hydrogens and an oxygen.
I hope that I helped but if this still makes no sense, or if I haven't explained it as well, then please don't hesitate to ask further questions. Thank you.
Answer: I'm gonna say the answer is Mutualism.
GAGTTA is what you have.
CTCAAT is what you’ll get.
A matches with T, G matches with C, and U is only for translating out of the DNA sequence.