(A) Devote
(B) Dedicate
(C) ** Resolve
(D) Decide
EXPLANATIONS BELOW
Concept note-1: -In math always try to understand every single line and never try to remember anything except some formulas. For your special case if you are struggling for passing it then don’t prepare all chapters but choose 70% chapters you find more easy and try yo understand basic concepts regarding those chapters.
Concept note-2: -Sometimes a student studies a lot but he gets lesser marks in exam because he may not be aware of test taking strategies which tells him how to express his learning in best way in exam or reproduce his learning in a good way in exam to convince the checker to give you more marks.