Photosynthesis and carbon fixation can only occur in the presence of light. true or false

True actually, Photosynthesis cannot take place in the absence of light however there are stages of Photosynthesis that are light independant and can carry on without light these phases are where Carbon fixation takes place, but in order for Photosynthesis to start light is required,

False. The photosynthesis process has two stages, one in presence of light and the other without the presence of light (dark fase), in fact, the carbon fixation can occur during the dark fase, this process is call Calvin cycle.