Which of the following groups has all three micro-elements?

Macronutrients are generally present in plant tissues in large amounts (in excess of $10 \text{ mmole kg}^{-1}$ of dry matter). The macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorous, sulphur, potassium, calcium and magnesium.

Micronutrients or trace elements are needed in very small amounts (less than $10 \text{ mmole kg}^{-1}$ of dry matter). These include iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel.

Analyzing the given options:
Magnesium (Mg), Potassium (K), Sulphur (S), and Calcium (Ca) are macronutrients.
Therefore, the groups in the first, third, and fourth options contain macronutrients.

Zinc (Zn) and Copper (Cu) are micronutrients, and Silicon (Si) is a beneficial trace element required by some higher plants. Since it does not contain any macronutrients, this is the most appropriate choice.

Answer: Zinc, Copper, Silicon