When platelets attach to collagen threads in an injured vessel the platelets swell, form extensions and then stick together. as a result of these steps what structure is formed?

Before the plug forms,  a platelet will stick to the blood vessel (adhesion), change its shape and signal other platelets to come help (activation and secretion). Then they stick to each other (aggregation).

there are plastid colour pigment organelle containing a verity of colours

              plastids contain of three organelles 1) chloroplast   (2)   chromoplast   (3)   lecoplast

            the verities of colours are present in chromoplast rather than green so, petals of sun flavour colour is due to chromoplast.

answer; i believe the correct answer is (a)0