Explanation:

- To determine when the bells will ring together again, we need to find the least common multiple (LCM) of their ringing intervals.

- The intervals are 15, 25, 35, and 45 minutes.

- The LCM of these numbers is 1,575 minutes.

- 1,575 minutes is equal to 26 hours and 15 minutes.

- Over 72 hours, 26 hours and 15 minutes will fit 2 complete times (because 3 times would exceed 72 hours).

- Therefore, the bells will ring together 2 more times in the next 72 hours.

Option:3 - 2