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 all the three figures - the circle, the square and the triangle and the third dot lies in the region common to the circle and the square only. In each of the figures (1) and (3), there is no region common to the circle and the square only and in fig. (2), there is no region common to the circle and the triangle only. Only fig. (4) consists of all the three types of regions.