Heidi must correctly answer at least 80% of the questions on an exam to advance to the next
level in her online course. Heidi has already correctly answered 26 questions and incorrectly
answered 4 questions. How many of the 15 questions remaining must Heidi correctly answer
to advance to the next level?
A. at least 10
B. at least 11
C. at least 12
D. at least 13