Which statement is true? a reflection is not a function because the image could overlap the pre-image. a reflection is a function because the line of reflection is always horizontal. a reflection is not a function because a point on the pre-image could be mapped to more than one point on the image. a reflection is a function because each point on the pre-image is mapped to exactly one point on the image.

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.