If atmospheric CO₂ concentrations increase twofold or more, how will plants be affected, disregarding any changes in climate?

A) All plants will experience increased rates of photosynthesis.
B) C₃ plants will have faster growth; C₄ plants will be minimally affected.
C) C₄ plants will have faster growth; C₃ plants will be minimally affected.
D) C₃ plants will have faster growth; C₄ plants will have slower growth.
E) Plant growth will not be affected because atmospheric CO₂ concentrations are never limiting for plant growth.