उत्तर : 3. "वैनेडियम एवं सोडियम"
व्याख्या :

A total of 16 nutrients are required for normal growth and development of plants. ,

• Plants obtain carbon, hydrogen and oxygen from air and water.

• Plants obtain nitrogen, phosphorus and potassium from the soil. ,

• Plants absorb calcium, magnesium and sulfur in small quantities.