The look of pure panic when you realize Leonhard Euler was basically the Thomas Edison of mathematics. The quiz question is hilariously impossible because Euler had his brilliant fingers in everything - fluid mechanics, continuum mechanics, and even laid groundwork for Lagrangian mechanics. Meanwhile, F=ma is Newton's second law, making it the only correct answer despite being the most basic formula on the board. That's the mathematical equivalent of asking "which of these isn't a Beatles song?" and including "Happy Birthday." The man invented so many formulas they ran out of letters and started using other alphabets. Some mathematicians just publish papers; Euler published entire branches of mathematics.