Interview questions where every wrong answer is explained

Sixty free questions, twenty each for JavaScript, Python and SQL. Every snippet was run before its answer was written down, so the output shown is what the interpreter or the database really printed. Pick an answer and you get the reason behind all four options, not only the right one.

This is a sample from 1,702 questions. The full banks are PDFs, questions first and the complete answer key after, with the same four explanations on every question.