What of the following is true for all parallelograms? Opposite sides are parallel. All four angles are congruent. All four angles are acute angles. All four sides are equal in length.

 a) Opposite sides are parallel

Step-by-step explanation:

a) In a parallelogram, opposite sides are parallel (which is why it is called a PARALLELogram).

b) Opposite angles are congruent (not ALL angles). The only parallelograms where all of the angles are congruent are Squares and Rectangles.

c) Consecutive angles are supplementary so their SUM must be 180°. Therefore if one angle is less than 90° (acute), the other angle must be greater than 90° so it is not possible that all angles are acute (∠ 90°).

d) The sides do not have to be equal.  The only parallelogram whose sides have equal lengths are Squares.

∠cbe and ∠deb are same-side interior angles.

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b. 2 and 4

step-by-step explanation: