From the perspective of the fluid leakoff mechanism of fracturing fluid, which kind of fluid leakoff coefficient mainly controls the effect of fracturing fluid's wall-forming property（ ）。 A: Reservoir fluid compression zone B: Fracturing fluid invasion zone C: Filter cake area D: Wellbore area

If there is no solid in the fracturing fluid, and fluid viscosit is close to the viscosity of formation fluid, which will dominate the leakoff? A: Wall builiding. B: Fracturing fluid viscosity. C: Compressibility of formation fluids. D: Compressibility of fracturing fluid.