This diagram is a straightedge and compass construction.
Select all true statements.
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Line E F is the bisector of angle BAC.
Line E F is the perpendicular bisector of segment BA.
Line E F is the perpendicular bisector of segment AC.
Line E F is the perpendicular bisector of segment BD.
Line E F is parallel to line CD.

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.