  The scalar potential, time component vector potential and flux tube quark
confinements are studied in this paper. We find that the predictions of scalar
confinement and time component vector confinement are in considerable conflict
with measured values while the flux-tube confinement works well to explain the
experimental data. We also study the relativistic flux tube model. From the
comparison of the exact numerical solution with the analytic approximation
solution for heavy-light mesons, we find that the solutions are much more in
agreement with each other for higher excited states since the deep radial limit
is better satisfied.
