The correct answer is option 3: Straight line.

A velocity-time graph shows the relationship between velocity and time for a moving object. When a car is moving with uniform acceleration, it means that its velocity is changing at a constant rate. In other words, the car is accelerating at a constant rate.

When an object is moving with uniform acceleration, the velocity-time graph will be a straight line. This is because the change in velocity is constant over time. As time increases, the velocity of the car increases at a steady rate, resulting in a linear graph.

The other options, parabola, logarithmic, and exponential, are incorrect. A parabolic graph represents an object under the influence of gravity, such as a projectile being thrown in the air. A logarithmic graph represents diminishing returns or a slowing rate of change, which is not the case when a car is moving with uniform acceleration. An exponential graph represents rapid growth or decay, which also does not match the behavior of a car moving with uniform acceleration.

Therefore, the correct nature of the velocity-time graph for a car moving with uniform acceleration is a straight line.