Mass flow hypothesis was put forward by

Answer: Option B

Mass flow hypothesis was put forward by Munch.
Theory to explain the movement of sap through the phloem. It was proposed by Ernst Munch, a German plant physiologist in 1930.
A high concentration of organic substances, particularly sugar, inside cells of the phloem at a source, such as a leaf, creates a diffusion gradient that draws water into the cells from the adjacent xylem.