Irregular demand refers to a demand situation where the market demand for certain goods or services fluctuates greatly in different seasons, different days of the week, or even different times of the day. According to the above definition, which of the following is an irregular requirement? ['Taxis are in short supply in the morning and evening rush hours.', 'An electric store celebrates a discount.', 'A museum introduces a group of Van Gogh paintings touring, and tourists flock.', 'A toothbrush of a certain brand is divided into soft, hard, and three types to target different consumers.']