Directions: Complete the following MCQ using an appropriate preposition.
My parent’s anniversary is ________ the 7th of May.

The correct answer is: On

The correct answer is "on".
We use the preposition "on" to convey the idea of either a point of contact or a specific measure of time, such as a date or a week. Here, the speaker is talking about the particular date of his parent's anniversary, that is, 7th of May.  Though no point of contact is mentioned here, a specific date has been mentioned to indicate a particular measure of time. So, the correct answer is "on".