Which of the following statements about trapezoids is true?
a. both pairs of opposite sides are parallel.
b. one pair of opposite sides is parallel.
c. opposite angles are equal.
d. opposite sides are equal.

The best and most correct answer among the choices provided by the question is the second choice, b. one pair of opposite sides is parallel. 
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Its d so thats how it would would back from 1.0 form three four two

Period is the time it takes for one “cycle” to complete. in the parent sine function, period is 2*pi since sin(0) = 0, sin(pi/2) = 1, sin(pi) = 0, sin(3pi/2) = -1, and sin(2pi) = 0. at that point, the sequence repeats itself. i’m not sure if your graph is similar to the sine function since you didn’t provide a picture, but you can find the period by looking at a graph.