Fixing Of Strike prices ?

In Options, stock Exchanges fix the strike price. At any given time there are 4-5 strike prices for any option.

Some of them In The Money, some of them Out Of The Money and one In The Money Option.

For instance if spot price is 3000, then strike prices are 2900, 2950, 3000, 3050, 3100.
Here two options are in the money, two out of the money and one near the money. Now if the spot price suddenly rises to 3125, then Stock Exchange introduces a strike price of 3150, so that at least one out of the money contract is available for call buyer.