Why Were Muscle Cells and Extracts the Best Choice for Krebs,Johnson

Multiple Choice

Why were muscle cells and extracts the best choice for Krebs,Johnson and Szent-Györgyi to elucidate the cyclic nature of the citric acid cycle?

A) The reactions of the cycle in muscle cells are more highly regulated,and therefore easier to study,than in other tissues.
B) Muscle cells have an unusually high concentration of the starting material,pyruvate.
C) In muscle the cycle intermediates are used almost exclusively for energy metabolism by the cycle and not for other reactions.
D) Muscle cells can more easily uptake oxygen than other cells,so monitoring the consumption of oxygen is easier for these cells.