Emotional labor: refers to the behavior of employees in the service industry who integrate personal emotions into the work process when they interact with customers face-to-face, and have a positive impact on customers, enterprises and service personnel themselves. Which of the following are emotional labor. ["An airline stewardess standing on both sides of the boarding gate welcomes passengers, and sometimes smiles and touches the child's head.", 'Xiao Liu always smiles and answers her calls kindly and enthusiastically. She has been rated as the most beautiful operator for many years.', 'A hotel\'s intelligent customer service "Xiao Qing" is empathetic and has a sweet voice. Guests staying at the hotel like to interact with her.', 'Xiao Qin has worked in the Letters and Calls Bureau for many years, and every time he receives visitors, he is very patient and understands the details in detail.']