Security thinking means making observations against the development of current things or events and making preparations for them after observation. Which of the following is security thinking? ['Xiao Li has been weak since childhood and has caught colds on both sides for three days. After ten years of winter swimming, he is now rarely sick.', "The company's operation is getting more and more difficult, Xiao Chen feels that he will definitely lay off staff, and quietly delivers several resumes to the talent market.", 'An old man with a humpback came on the bus. Xiao Wang gave up his seat to the old man because he was afraid of falling and injured.', 'The temperature has plummeted in these two days. Lao Zhang is going on a business trip to the north. His wife deliberately stuffed a few thick clothes into his suitcase.']