The Latin root tactus is part of the word tangent. What does the word tangent mean?

touching

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Explanation:

tan·gent  

noun: tangent; plural noun: tangents

1.  a straight line or plane that touches a curve or curved surface at a point, but if extended does not cross it at that point.

2.  a completely different line of thought or action.

"he quickly went off on a tangent about wrestling"

3.  MATHEMATICS  the trigonometric function that is equal to the ratio of the sides (other than the hypotenuse) opposite and adjacent to an angle in a right triangle.

adjective: tangent

(of a line or plane) touching, but not intersecting, a curve or curved surface.

"this curve is tangent to the average cost curve"

ITS TOUCHING

answer; i believe the correct answer is ( indirect characterization);

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).