Blackman demonstrated that increasing illumination increased the photosynthetic rate up to a point when $CO_2$ becomes limiting. If light was not limiting,temperature becomes limiting. Emerson found that maximum $CO_2$ fixation could be achieved with brief flashes of light. Mark the correct statement in the following:

• A
  Only one factor can be limited in photosynthesis
• B
  Photosynthesis consists of a light and dark reaction
• C
  The trapping of light by chloroplast is temperature dependent
• D
  The trapping of light by chloroplast can occur only if $CO_2$ is present