Identify the correct statements.

A. All tsunamies are seismic sea waves.

B. As the tsunami approaches shore its velocity drops and the wave height greatly increases.

C. Modern tsunami warning systems depend on sea-bed seismometers and submerged devices and satellites.

D. In open sea, lack of steepness and tsunami wave's very long period causes slow and imperceptible crest rise.

Choose the correct answer from the options given below: