There are only two ways to gather information from human subjects about what they are currently doing, thinking, or feeling. One way is to【C1】______ what they do, the technique of observation the【C2】______ is to ask them, the technique of surveys. Many【C3】______ included in each type of technique【C4】______ several advantages and【C5】______ . Firms frequently use【C6】______ techniques to minimize【C7】______. There is a great variety of observational studies. A researcher stands near the entrance【C8】______ a theatre and observes the approximate age and sex of patrons【C9】______ the theatre during certain times of the day and days of the【C10】______. Researchers comb through the garbage【C11】______ of Arizona residents to【C12】______ what is being thrown【C13】______ and, by inference from packages,【C14】______ is being bought. Toy manufacturers watch【C15】______ behind one-way mirrors to see how children【C16】______ to and play【C17】______ prototypes(样品) of toys they are thinking of introducing. Observers in public places -- airports,【C18】______ offices -- watch to see【C19】______ subjects read newspapers and magazines. Researchers call【C20】______ households and take a 'pantry audit' to learn the quantity and brands of certain items on the kitchen or bathroom shelves. 【C1】