Plant A is supplied with : 

Nomal Carbon dioxide and Water, laballed with radioactive oxygen atoms 

Plant B is supplied with:

Carbon dioxide,labelled with radioactive oxygen atoms and Normal Water 

Which photosynthetic product of Plant A will contain radioactivity and which photosynthetic product of Plant B Will contain Radioactivity? Predict with reasons.

Hi Kristy, you will be asked what you know so far before anyone will help you. Welcome to the forum.

Hi, I think it involves both the light-dependent reaction and in-independent reaction of photosynthesis. 

I'm sure someone will come along but in the meantime see if this helps and see if you can track the path of the radioactive elements into which end products:

http://www.rsc.org/Education/Teachers/Resources/cfb/Photosynthesis.htm

 

@OP, Why not write out the light-dependent and light-independent reactions for us? Then we can discuss them.