A good lubricant should be highly

Options

A. Viscous
B. Nonvolatile
C. Both
D. None

Answer

To determine the correct answer to the question "A good lubricant should be highly," we need to analyze the characteristics of a good lubricant. Here’s a step-by-step solution:

### Step 1: Understand the Properties of a Good Lubricant
A good lubricant should have certain essential properties to function effectively. These properties include:

1. **High Boiling Point**: This ensures that the lubricant remains in liquid form even at high temperatures.
2. **Low Freezing Point**: This allows the lubricant to remain effective at low temperatures.
3. **High Viscosity Index**: A high viscosity index indicates that the lubricant's viscosity changes very little with temperature, which is crucial for maintaining performance across a range of temperatures.
4. **Thermal Stability**: This means the lubricant should not break down or lose its properties when exposed to heat.

### Step 2: Analyze the Options
Given the options:
- A) Viscous
- B) Non-volatile
- C) Both A and B
- D) None

We need to determine which of these properties is essential for a good lubricant.

### Step 3: Evaluate Each Option
- **Option A (Viscous)**: High viscosity is indeed a critical characteristic of a good lubricant. It helps in reducing friction between surfaces.
- **Option B (Non-volatile)**: While non-volatility is beneficial, it is not as critical as viscosity in defining a good lubricant.
- **Option C (Both A and B)**: Since non-volatility is not as essential as viscosity, this option is not the best choice.
- **Option D (None)**: This option is incorrect as we have established that viscosity is important.

### Step 4: Conclusion
Based on the analysis, the most important characteristic of a good lubricant is that it should be highly viscous. Therefore, the correct answer is:

**Answer: A) Viscous**