Dimorphic chloroplasts occur in
Chloroplast of C4 plants is dimorphic chloroplast because it shows two different types of the chloroplast.
1). The chloroplast with grana
2). Chloroplast without grana and surrounded to the vascular bundle.
The chloroplast is of 2 different types hence it's called as the dimorphic chloroplast. And it is best seen among sugarcane of the C4 plants.
So, the correct option is 'Sugarcane'.