Plants make proteins by using a) oxygen, glucose and water b) carbon dioxide, water and sunlight c) nitrogen compounds, water and oxygen d) carbon dioxide, water and nitrogen compounds

Proteins are made of amino acids, which contain carbon, hydrogen, oxygen, and nitrogen.

• Plants obtain carbon, hydrogen, and oxygen from carbon dioxide ($\text{CO}_2$) and water ($\text{H}_2\text{O}$) through photosynthesis to create sugars (carbohydrates). These sugars provide the carbon backbone for amino acids.
• Plants obtain nitrogen from the soil in the form of nitrogen compounds (e.g., nitrates, ammonium ions). This nitrogen is incorporated into the carbon backbone to form amino acids.

• a) oxygen, glucose and water: Oxygen is a product of photosynthesis, not a raw material for protein synthesis. Glucose is a product, not a primary raw material in this context.
• b) carbon dioxide, water and sunlight: These are the inputs for photosynthesis, which produces carbohydrates. This option lacks nitrogen, which is crucial for proteins.
• c) nitrogen compounds, water and oxygen: Oxygen is not used for protein synthesis.
• d) carbon dioxide, water and nitrogen compounds: Carbon dioxide and water provide the carbon, hydrogen, and oxygen for the carbon skeletons (via photosynthesis), and nitrogen compounds provide the essential nitrogen. This combination allows for the synthesis of amino acids and subsequently proteins.

The correct option is D.

• D. carbon dioxide, water and nitrogen compounds