Holly begins with 1 penny in her piggy bank. She adds 2 pennies on day 1, 4 pennies on day 2, and 8 pennies on day 3. She continues this pattern for 30 days. Which statement describes why this sequence is a function?

Select EACH correct answer.

a Each amount of pennies corresponds to a unique day in this sequence.
b The graph of this sequence would pass the horizontal line test.
c Each day corresponds to a unique amount of pennies in this sequence.
d The graph of this sequence would pass the vertical line test.