A helium-filled balloon is attached to the floor of a car by a light string. The car is initially at rest and then begins to accelerate forward with a constant acceleration \(a\). An observer standing on the sidewalk and an observer sitting in the car both note the behavior of the balloon. Which of the following correctly describes the direction the balloon tilts relative to the car and provides a correct physical justification?

Consider the density of the air inside the car to be \(\rho_{air}\) and the density of the helium to be \(\rho_{He}\), where \(\rho_{air} > ho_{He}\).