The correct option is C Teak and pine
Secondary growth is observed in dicots and gymnosperm. It is not observed in pteridophytes and rarely observed in monocots. Secondary growth results in increase in girth or diameter of the stem by formation of secondary tissue by the activity of lateral meristem. So for study of secondary growth, teak (angiosperm) and pine (gymnosperm) are best suited. In wheat, fern and sugarcane there is no secondary growth. So, option C is correct.