aidebaobao

call options are pos from 0 to 1 and the closer to expiration in the money calls will be close to 1

put option are neg from 0 to -1 and the closer to expiration in the money puts will be close to -1

delta measures the correlation b/w the changes in option prices and the underlying, so for puts for example will increase in price as the underlying price falls (this is why the delta is negative - b/c the price change is negatively correlated with the price change of the underlying)

now for options that are at the money near expiration these jump back and forth b/w 0 and 1 b/c if the price of the underlying ends up below the strike for a call there is no change in price in the option b/c there is no value in holding an out of the money option (so the correlation is 0). however once the price of the underlying moves above the exercise price (and again this is near expiration) the value ov the call is going to increase nearly in step with the price of the underlying (so the correlation is very close to 1).