The best explanation for why your body continues to move forward when you trip, while your foot suddenly stops, is: An unbalanced force stops your foot but does not act on the rest of your body.
This statement accurately reflects the situation where the foot encounters an obstacle (the unbalanced force), causing it to stop, while the rest of the body, due to inertia (the tendency of an object to resist changes in its state of motion), continues moving forward until it is acted upon by another force.