Which technological advance enabled Calvin to perform his lollipop experiment on the light-independent reactions of photosynthesis in 1949?

A. Methods for tracing radioactive carbon incorporated in molecules produced by the alga Chlorella

B. Development of electron microscopes enabling the molecules produced by the alga Scenedesmus to be viewed

C. Methods for changing the wavelength of light shining on the alga Scenedesmus contained in the lollipop

D. Development of X-ray diffraction techniques enabling the molecules produced by the alga Chlorella to be identified

A