How we check our practice questions

Who writes each question, and from what

Every question is drafted and checked with artificial intelligence (AI). When this page says a reviewer, verifier or checker, it means an AI review run apart from the one that wrote the question. No expert and no exam agency has approved the questions.

Each question is written in our own words from a public source: TCEQ’s rules, TCEQ’s guides or a publication from another government agency, such as the EPA. After you answer, the question shows its source, with a link. We never use questions anyone remembers from the exam.

The check of each question

A separate review, not the one that wrote the question, checked it against its source: the answer, the other options, the explanation, and that the Spanish says what the English says. Each question was approved, fixed and checked again, or rejected. Only approved questions reach the practice.

• In November 2026, verifiers who did not write them checked all 300 questions in OperadorListo's Class D water bank against their sources.[1]
• 114 of the 294 questions on the site were corrected (an explanation, a citation or the Spanish) and checked again before being approved.[1]
• 6 of the 300 questions were rejected and are left out of the site: 3 in the review and 3 later, in another review.[1]

A blind check of a sample

• After the verifiers finished, a separate checker drew 100 approved questions at random and checked each one again from scratch against its source.[1]
• In that sample of 100, the checker found 0 questions with a wrong answer key, a wrong number or a false statement.[1]
• In that sample of 100, the checker found 2 small issues: a page number in a citation, which was fixed, and one question whose right answer stood out by its length, which was later rejected and is left out of the site.[1]

A sample of 100 questions[1] with no serious error does not prove there are none in the whole bank. Some may remain.

The math problems

A program builds the math problems with new numbers each time. A second program, written separately, solves each one again from its inputs alone and compares its result with the key.

• A separate solver re-solved 160,000 generated math problems (16 problem types × 5,000 each, in Spanish and in English) and agreed with every answer key.[2]

When a law changes

Each question keeps the date its source was read. We have not yet done a separate review of every change to TCEQ’s rules; the blind check read each rule as it reads today.

• In the blind check of 100 questions, every Texas rule those questions test was read in its current text, including the sections amended effective December 21, 2023, January 9, 2025 and March 23, 2025.[1]

If you see a mistake

Write to hola@operadorlisto.com with the question and what you saw. We check it against its source, then fix it or take it out.