Step 1: Understanding the Concept:
This question tests the correct preposition for the phrasal verb 'take care'.
Step 2: Detailed Explanation:
The phrasal verb "take care of" means to look after, to keep someone or something safe and in good condition.
It is a fixed expression. For example: "She takes care of her younger sister." or "You must take care of your belongings."
Step 3: Applying to the Sentence:
The sentence expresses the need to look after 'our health'. The correct phrasal verb to express this is "take care of".
Step 4: Final Answer:
The correct preposition is of.