I don't know much about this, but probably the reason why your teacher circled 300k is because of what's in the photo below. If you couldn't tell from the photo, its because 300k isn't negative. Anyway this is my guess, based on my limited knowledge.
Answer:
c. The reactant that is used up before the others
Explanation:
b. is also correct, because the limiting reactant is completely used up.
a. and d. are wrong. They describe the excess reactant.
Potassium sulfite<span> (K</span>₂<span>SO</span>₃<span>)
hope this helps!</span>
