A student's test score is at the 75th percentile. What does this mean?

A percentile tells where a score ranks within a group. Being at the 75th percentile means that about $75\%$ of the scores are at or below this student's score, so choice G is correct. Choice F confuses the percentile with a percent-correct score; a student at the 75th percentile could have answered any share of the questions correctly. Choice H confuses it with a raw score of $75$ points. Choice J reverses the meaning: roughly $25\%$ of scores are at or above this student's score, not at or below it. Percentiles describe rank, not accuracy.