C). If you want, you can modify the plan to better suit your needs.
Explanation:
As per the question, option C employs the word 'modify'(in verb form) appropriately as in this sentence 'If you want, you can modify the plan to better suit your needs', the word 'modify' implies the meaning 'to change, modify, or moderate' the plan as per the needs. The other options either employ the word inappropriately or uses incorrect form of the word(as in options A, B, and D). Thus, <u>option C</u> is the correct answer.
