Explanation:

To calculate this, we should take the L.C.M. of 6, 8, 12 and 18.

L.C.M. of 6, 8, 12, 18 = 72.

So, the bells ring simultaneously every 72 minutes.

In 6 hours (360 minutes) bells ring simultaneously 5 times (72, 144, 216, 288, 360 mins).

Including the simultaneous ring at 12'O clock, the answer is 6 times.

Though first bell rang at 12 o' clock and then 5 times, hence bell ring 5+1=6 times in 6 hours.

Hence, option 1 is the correct answer.