The following sentence has been divided into parts. One of them may contain an error.
Writing down your thoughts / can has immense positive / effects on your health.

Correct option is C

Option (c) contains an error.
Explanation: The phrase “can has” is grammatically incorrect. After a modal verb like can, the base form of the verb should be used. Hence, "has" should be replaced with "have".
Correct sentence: Writing down your thoughts can have immense positive effects on your health.
Grammatical rule used: After modal verbs (can, could, may, might, shall, should, will, would, must), the base form of the verb is always used.
Example:
· Incorrect: She can goes to school.
· Correct: She can go to school.