Matias is an intermediate-level ESOL student from Brazil who has lived in the United States for 2 years. Next week, he will take a History test, and his teacher located a version of the test in Portuguese. However, Matias failed the test. What is the most likely explanation for Matias' poor performance on the translated test?
a. Lack of language proficiency in Portuguese
b. Lack of subject matter knowledge
c. Difficulty understanding the test format
d. Test anxiety