9. Select all the statements that must be true. Parallelograms have four congruent sides

Both sets of opposite sides of a parallelogram are parallel and congruent

A trapezoid is a parallelogram

Diagonals of a parallelogram bisect each other

Diagonals of a parallelogram are congruent​

Explаnation is in а file

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a) one student is chosen from classroom a, then a student is chosen from classroom b.  

step-by-step explanation:

independent events are ones in which the probability of one event does not affect the probability of the second event.

one student is chosen from classroom a; this does not affect the chances of choosing a student from classroom b.   this makes these independent events.

when one card is chosen from a standard deck and then set aside before a second card is chosen, the probability of the second card being chosen changes.   this makes them dependent events.

when one student is chosen from classroom a and then a second student is chosen from classroom a, the probability of choosing the second student changes.   this makes them dependent events.

when a letter is chosen from the alphabet and then a second letter is chosen, the probability of choosing the second letter changes.   this makes them dependent events.