## **Core Concept**
The problem involves understanding the principles of hemodynamics, specifically the relationship between blood pressure, resistance, and flow in vascular circuits. The equation that governs this relationship is (Q = frac{P_{in} - P_{out}}{R}), where (Q) is the flow, (P_{in}) is the inflow pressure, (P_{out}) is the outflow pressure, and (R) is the resistance. In a parallel circuit, the total resistance ((R_{total})) is given by (frac{1}{R_{total}} = frac{1}{R_1} + frac{1}{R_2} + frac{1}{R_3} + frac{1}{R_4} + frac{1}{R_5}).

## **Why the Correct Answer is Right**
Given that each of the parallel circuits (R1, R2, R3, R4,) and (R5) has a resistance of 5 mm Hg/mL/min, we first calculate the total resistance ((R_{total})) of the parallel circuit. The formula for the total resistance of resistors in parallel is (frac{1}{R_{total}} = frac{1}{R_1} + frac{1}{R_2} + frac{1}{R_3} + frac{1}{R_4} + frac{1}{R_5}). Substituting the given values: (frac{1}{R_{total}} = frac{1}{5} + frac{1}{5} + frac{1}{5} + frac{1}{5} + frac{1}{5} = 1). Therefore, (R_{total} = 1) mm Hg/mL/min. The inflow pressure ((P_{in})) is 100 mmHg and the outflow pressure ((P_{out})) is 10 mmHg. Using the equation (Q = frac{P_{in} - P_{out}}{R_{total}}), we substitute the given values: (Q = frac{100 - 10}{1} = frac{90}{1} = 90) mL/min.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not match the calculation based on the correct formula for resistance in parallel and the subsequent flow calculation.
- **Option B:** This option is incorrect for the same reason as Option A; it does not align with the proper calculation of total resistance and flow.
- **Option C:** This option suggests a flow of 18 mL/min, which would not be correct given the low total resistance calculated from the parallel resistors and the significant pressure gradient.
- **Option D:** This option is incorrect because, like Options A and B, it does not correspond to the calculated flow based on the provided resistances and pressure gradient.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that in a parallel circuit, the total resistance is less than any of the individual resistances, which leads to a higher total flow than if the resistances were in series. This principle is crucial in understanding how blood flow is regulated in the cardiovascular system, particularly in the distribution of blood flow to different organs.

## **Correct Answer:**
. 90 mL/min