You Are Growing C₃ and C₄ Plants in Normal (21%)

You are growing C₃ and C₄ plants in normal (21%) and low (1%) O₂ air, under both warm, well-lit conditions and cool, shady conditions. You find that, in general, the C₃ plants have a photosynthetic advantage over C₄ plants in:

A) warm high light at 1% O₂ and cool shade at 21% O₂ only.
B) cool shade under 21% and 1% O₂, and in warm high light at 1% O_2.
C) cool shade at 21% O₂ and warm high light at 21% O_2.
D) warm high light at 21% O₂ and 1% O₂, and cool shade at 21% O_2.