Assertion : Mountain roads rarely go straight up the slope. Reason : Slope of mountains are large therefore more chances of vehicle to slip from roads.

Options

A. Statement-I is true, Statement-II is true, Statement-II is correct explanation for Statement-I
B. Statement-I is true, Statement-II is true, Statement-II is NOT a correct explanation for Statement-I
C. Statement-I is true, Statement-II is false
D. Statement-I is false, Statement-II is true.

Answer

To analyze the given assertion and reason, we will break down the statements step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that mountain roads rarely go straight up the slope. This implies that the design of these roads is influenced by the steepness of the mountain.

**Hint**: Think about how roads are constructed on steep terrains.

2. **Understanding the Reason**:
- The reason provided is that the slopes of mountains are large, which increases the chances of vehicles slipping from the roads. This suggests that the steepness of the slope affects vehicle stability.

**Hint**: Consider the factors that contribute to vehicle stability on inclined surfaces.

3. **Analyzing the Relationship**:
- When a road goes straight up a steep slope, the angle of inclination (θ) increases. A larger angle θ results in a decrease in the normal force acting on the vehicle, which in turn reduces the frictional force available to keep the vehicle on the road.

**Hint**: Recall the formula for frictional force and how it depends on the angle of inclination.

4. **Frictional Force Calculation**:
- The frictional force (F_r) can be expressed as:
\[ F_r = \mu_n \cdot N \]
where \( N = mg \cos \theta \) (normal force), and \( \mu_n \) is the coefficient of friction. As θ increases, \( \cos \theta \) decreases, leading to a decrease in normal force and thus frictional force.

**Hint**: Remember that friction is what prevents slipping; less friction means a higher chance of slipping.

5. **Conclusion**:
- Since the assertion states that mountain roads do not go straight up due to the high chances of slipping (as indicated by the reason), both statements are correct. The reason accurately explains why the assertion is true.

**Hint**: Reflect on how both statements are interconnected and support each other.

### Final Answer:
Both the assertion and reason are correct, and the reason is the correct explanation for the assertion. Therefore, the correct option is A.