Answer:
b. the theory of blending inheritance
Step-by-step explanation:
Before Mendel's work was completed and published, theory of blending inheritance was widely accepted. According to it traits from both parents were blended and expressed in the next progeny. The new trait wont be in extreme like its parents' and would fall somewhere in between the spectrum.
Mendel disproved theory of blending inheritance by his famous pea experiment. When he crossed a pure breeding tall and pure breeding dwarf pea plant he got all tall pea plants in next progeny. According to theory of blending inheritance, the height of pea plants in next progeny should have been a result of mixing of heights from the two parent plants. But all the plants were tall like one of the parent plant disapproving the theory.