Photosynthesis rates limited by light and CO2

Steps:

• Identify that photosynthesis rate depends on light intensity and CO2 concentration as limiting factors.
• Recall rate increases with each factor until saturation, forming a plateau.
• Expect graphs showing initial rise then leveling off for both variables.
• Select graph matching this pattern without reversal or linear trends.

Why A is correct:

• Matches limiting factor principle: rate rises hyperbolically with light/CO2 then plateaus per Blackman's law of limiting factors.

Why the others are wrong:

• B shows linear increase without plateau, ignoring saturation.
• C depicts rate decrease at high levels, contradicting positive dependence.
• D combines unrelated trends, not isolating light/CO2 effects.

Final answer: A