f. both a and d
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Macronutrients are substances that are required by plants in amounts greater than 0.5 percent of the plant's dry weight. There are nine macronutrients for plants: carbon, oxygen, hydrogen, nitrogen, potassium, phosphorus, calcium, magnesium, and sulfur. Additionally, plants also need seven additional micronutrients: boron, chlorine, copper, iron, manganese, molybdenum, and zinc.