Although the computer has strong functions in many aspects, experiments have shown that operating the computer is faster and more accurate than using an abacus when calculating addition, subtraction, multiplication, and division. Which of the following, if true, could greatly weaken the persuasiveness of the above experiment? ? ['The person who operates the computer and uses the abacus in the experiment must be different people.', 'Abacus can use tips.', 'When using an abacus, you can use mental arithmetic, but a computer operator cannot.', "Use a computer for calculations, don't care about the size of the number, but not the abacus. In the experiment, only the smaller numbers are calculated."]