Most probable chance of developing caries in the following curve is at:
Point A
Point B
Point C
Point D
It is Stephen's curve, which is used for illustration of rapid decrease in pH after sucrose consumption. Exposure of dental plaque to a fermentable carbohydrate leads to decrease in pH rapidly,  reaching minimum in approx. 5-10 minutes. It recovers to its initial value in 20-60 minutes gradually.