Answer is (4) because:
Triangle: the young plants travel the furthest from parent plant in fig 1 & is spread out all over
Star: the young plants are clustered around the parent plant – splitting action cannot throw the seeds very far away from the parent plant, so the young plants are usually still near the parent plant
Cylinder: This is the tricky one – usually, the young plants near the river are dispersed by water. But the clue is that some of the young plants are up-river from the parent plant, therefore it cannot be dispersed by the water (since water cannot push the seeds upriver). So it has to be dispersed by animals, which can cross the river (or go upriver to disperse the seeds down again).