Answer:
If the underlined word is precursor, the answer would be preceding.
Step-by-step explanation:
Using clues around the word, I was able to figure out that Algebra comes before Calculus. Looking at the choices, the only one that would fit is preceding because the others' definitions don't mean anything close to precursor. Precursor means to come before another thing that is close, if not, the same. If it's not preceding, it would be introduction.