Final answer:
Ebb tide is the falling tide, flood tide is the rising tide, and slack tide is the period of no change in tide velocity.
Step-by-step explanation:
Tides are the alternate rising and falling of the sea level caused by the difference in the strength of the Moon's gravitational pull on different parts of the Earth. Ebb tide refers to the falling or outgoing tide, when the water level is decreasing. Flood tide, on the other hand, is the rising or incoming tide, when the water level is increasing. Slack tide is the period when the water is neither ebbing nor flooding, and the tide is at its lowest velocity.