The correct answer is 3 (بـ).
Here's the breakdown:
في (fi) means "in" and is commonly used for times of day and months.
على (ala) means "on" and is typically used for days of the week and dates.
قبل (qabla) means "before" and could be used with times if you're specifying a time before another specific time, but wouldn't be used for "lunchtime."
Therefore, "بـ (bi)" is the most appropriate preposition to use in this context, indicating the specific time of "lunchtime."