Many members of political parties … to opposing parties just before elections.

Analyze the question The sentence is about political party members who move from their party to opposing parties just before elections. We need the word that best describes this specific action, followed by the preposition "to".

Explain the concept "Defect" means to abandon one's own party, country, or cause in order to join an opposing one. It is the standard word for switching political allegiance, and it takes "to": defect to another party.

Check each option

• A. depart: means to leave. It takes "from" (depart from a place), not "to" an opposing party. It does not carry the idea of switching sides.
• B. change: you "change parties" or "change to" something, but it is a general word. It lacks the sense of abandoning one side for a rival.
• C. defect: fits perfectly. "Defect to opposing parties" is the exact, idiomatic usage.
• D. go: grammatically possible ("go to opposing parties") but vague. It does not express the political betrayal or switching of allegiance implied.

Solution "Many members of political parties defect to opposing parties just before elections."

Tip: In "best completes" questions, choose the most precise word, not just one that is grammatically acceptable. Remember the pairing "defect to", which is common in Nigerian political news (e.g., "defected to the APC/PDP").