Which of the following did the scientist Melvin Calvin use to discover the biosynthetic pathway of photosynthesis?

What is the by-product of bacterial photosynthesis?

$PGA$ as the first carbon dioxide fixation product was discovered in photosynthesis of

The law of limiting factors in photosynthesis was proposed by Blackman in $1905$. Which of the following scientists criticised this law?

The carbon isotope used for the study of photosynthesis is ........

Variegated leaves of a plant were supplied with radioactive carbon dioxide $(^{14}CO_2)$ during an experiment. Leaf $X$ was kept in the dark and leaf $Y$ was kept in the light. At the end of the experiment,the radioactivity in the leaves was measured and found to be as shown in the diagram. What is the most likely explanation for the level of radioactivity found in the yellow zone of leaf $Y$?