With high school students across the country steeped in Advanced Placement exams this month, some may wonder exactly what they are being tested on.

In Montgomery County, the most popular AP exam appears to reflect a little of the Washington region itself: U.S. government and politics. For each of the last three years, it has been the only AP exam given in Montgomery with more than 4,000 takers, according to district figures.

Nationally, English language and composition is at the top of the list, with U.S. history not far behind.

Here’s a look at the most recent exam numbers, for tests given last May, across a sampling of subjects in Montgomery County:

*521 in computer science

*594 in microeconomics

*910 in chemistry

*1,061 in Spanish

*1,327 in environmental science

*1,502 in biology

*1,567 in statistics

*1,668 in calculus AB

*1,685 in U.S. history

*2,767 in English literature and composition

*3,049 in world history

*3,464 in psychology

*3,781 in English language and composition

*4,088 in U.S. government and politics

The highest percentages of passing scores in Montgomery last year were in chemistry, microeconomics, calculus BC and computer science. On each of these exams, more than 80 percent of students received a score of 3 or better on a five-point scale.

Participation in AP courses is widely viewed as a strong indicator of readiness for higher education, and exam success can lead to college credit.

In all, Montgomery gave 33,642 AP exams last May, its highest number. Some students take multiple AP exams in a given year.