Collegeboard 2020 MC Reflection

Reflection for 2020 Practice Exam MC on Collegeboard

• 4 min read


Today, I took the 2025 practice multiple-choice exam on Collegeboard and I received a score of 62/67.

Here’s what I got wrong and an explanation of the correct answer:


Question 16 (Skill 4.C)


A student wrote the following program to remove all occurrences of the strings "the" and "a" from the list wordList. While debugging the program, the student realizes that the loop never terminates. Which of the following changes can be made so that the program works as intended?


Answer: D

Inserting `index ← index - 1` between lines 7 and 8


I chose answer B, which is Inserting index ← index + 1 between lines 7 and 8. However, this is incorrect because the index starts at the end of the wordlist, not the start, so it must decrease in value after each iteration to go down the wordlist.


Question 40 (Skill 5.D)


Which of the following best explains how a certificate authority is used in protecting data?


Answer: D

A certificate authority verifies the authenticity of encryption keys used in secured communications.


I chose answer B, which is A certificate authority issues passwords that grant access to secure databases. However, this is incorrect because a certificate authority is used to validate the authenticity of encryption keys, not to issue passwords.


Question 47 (Skill 1.A)


The procedure BinarySearch (numList, target) correctly implements a binary search algorithm on the list of numbers numList. The procedure returns an index where target occurs in numList, or -1 if target does not occur in numList. Which of the following conditions must be met in order for the procedure to work as intended?


Answer: C

The values in numList must be in sorted order.


I chose answer B, which is The list numList must not contain any duplicate values. However, this is incorrect because a binary search does not depend on whether the list contains duplicate values, but the list must be sorted for target to be able to be located in numList.


Question 50 (Skill 1.D)


Consider the following algorithms. Each algorithm operates on a list containing n elements, where n is a very large integer. Which of the algorithms run in reasonable time?


Answer: D

I, II, and III


I chose answer A, which is I only. The first choice is correct because the elements are accessed in 2n time, however, the second choice is also correct because the elements are accessed in n^2 time, and the third choice is also correct because the elements are accessed in n time.


Question 67 (Skill 4.C)


The procedure NumOccurrences is intended to count and return the number of times targetWord appears in the list wordList. The procedure does not work as intended. For which of the following code segments will the call to NumOccurrences NOT return the intended value? Select two answers.


Answer: A & B

treeList <-- ["birch", "maple", "birch"]
numOccurrences(treeList, "birch")

treeList <-- ["birch", "maple", "oak"]
numOccurrences(treeList, "maple")


I chose answers B and D. Answer D has an array of ["birch", "maple", "oak"] and calls numOccurrences(treeList, "spruce"). This still returns the intended value because "spruce" does not appear in treeList at all, thus count will never change and will be displayed at 0.


My Learnings

Through my completion of the quiz, I was able to learn a lot about both the expectations from this cource, and where I stand as a CS student. Mainly, I was able to understand what a College Board MCQ is really like, and what types of questions they tend to ask. I also was able to see how well I currently understand the curriculum, and while I did achieve a decent score, I feel that I have room to improve in both my efficiency and logical approach. I learned that College Board has 5 big ideas for the class:

  • Creative Development
  • Data
  • Algorithms and Programming
  • Computer Systems
  • Impact of Computing


Wrapping up

I need to familiarize myself with topics such as time complexity, like in question 50, and certificate authority, like in question 40. I also missed a few questions because I did not spend enough time thouroughly reading each answer choice, which is why I missed 16, as I had thought that the index value was increasing and not decreasing. Overall, this MCQ shows that I should slow down on each question and familiarize myself with non-programming topics.

Compared to the last practice test I took, I did much better and improved on topics such as citizen science and encryption which I had trouble on last trimester.

Overall, I improved on:

  • Data Compression (67% to 100%)
  • Variables and Assignments (67% to 100%), Iteration (50% to 100%)
  • Digital Divide (0% to 100%)
  • Safe Computing (33% to 67%).

So far, I still have not encountered these, but I can practice with other MCQs to understand these topics:

  • Skill 4.A: Explain how a code segment or program functions
  • Skill 6.A: Collaborate in the development of solutions
  • Skill 6.B: Use safe and secure methods when using computing devices


2020 vs. 2018