**Core Concept**
The Michaelis-Menten hypothesis is a fundamental concept in enzymology that describes the kinetics of enzyme-catalyzed reactions. It explains how enzymes accelerate chemical reactions by lowering the activation energy required for the reaction to proceed. The hypothesis focuses on the formation of an enzyme-substrate complex, which is essential for the enzymatic reaction to occur.

**Why the Correct Answer is Right**
The Michaelis-Menten hypothesis states that the enzyme-substrate complex formation is a crucial step in the enzymatic reaction. When an enzyme binds to its substrate, it forms a complex that is more reactive than the substrate alone. This complex then undergoes a chemical transformation, resulting in the product formation. The enzyme-substrate complex formation is essential because it increases the reaction rate by lowering the activation energy and providing a more favorable environment for the reaction to occur. The enzyme-substrate complex is stabilized through non-covalent interactions, such as hydrogen bonding, ionic interactions, and hydrophobic interactions, which facilitate the catalytic process.

**Why Each Wrong Option is Incorrect**
**Option A:** The rate of enzymatic reaction is not independent of substrate concentration. According to the Michaelis-Menten hypothesis, the reaction rate is dependent on the substrate concentration, and it reaches a maximum value (Vmax) at high substrate concentrations.

**Option B:** The Michaelis-Menten hypothesis does not describe non-enzymatic reactions. It specifically focuses on enzyme-catalyzed reactions, where the enzyme plays a crucial role in accelerating the reaction rate.

**Option C:** Km is not the enzyme-substrate complex association constant. Km is the Michaelis constant, which is a measure of the enzyme's affinity for its substrate. It represents the substrate concentration at which the reaction rate is half of the maximum rate (Vmax/2).

**Clinical Pearl / High-Yield Fact**
The Michaelis-Menten hypothesis is a fundamental concept in understanding enzyme kinetics and catalysis. It is essential to remember that enzyme-substrate complex formation is a crucial step in enzymatic reactions, and it is responsible for increasing the reaction rate by lowering the activation energy.

**✓ Correct Answer: D. Enzyme substrate complex formation is essential in enzymatic reaction.**