Non Verbal Reasoning - Dot Situation - Discussion

In fig. (X), one of the dots lies in the region common to the circle and the triangle only, another dot lies in the region common to the circle, the square and the triangle only and the third dot lies in the rectangle alone. In figures (1) and (4) there is no region common to the circle and the triangle only. In fig. (3) there is no region which lies in the rectangle alone. Only fig. (2) contains all the three types of regions.