Which kind of plastid is more common in

(a) roots of the plant (b) leaves of the plant (c) flowers and fruits

(a) Leucoplasts in roots
Leucoplast is a colourless organelle found in plant cells, used for the storage of starch.

(b) Chloroplasts in leaves
Chromoplasts are coloured plastids other than chloroplasts. Plastids are a class of small organelles.

(c) Chromoplasts in flowers and fruits.
Chloroplasts are the plastids that contain chlorophyll and the process of photosynthesis takes place in it.