题目内容：
根据下列材料回答 题。Passage Five
Some years ago industries had more freedom than they have now，and theyDid not need tobe as careful as they must today．TheyDid not need to worry a lot about the safety of the newproducts that theyDeveloped．TheyDid not have to pay much attention to the health and safetyof the people who worked for them．Often new products wereDangerous for the people who usedthem；often conditions in the work place had very bad effects on the health of the workers．
Of course sometimes there were realDisasters which attracted the attention of governmentsand which showed need for changes．Also scientists who wereDoing research into the health ofworkers sometimes produced information which governments could not ignore．At such times，there were inquiries into the causes of theDisaster or the problems．New safety rules were oftenintroduced as a resuIt of these inquiries；however，the new rule；came too late to protect thepeople whoDied or who became seriously ill．
Today many governments have specialDepartments which protect customers and workers.In the U．S．，for example，there is aDepartment which tests new airplanes and gives warningsabout possible problems．It also makes the rules that aircraft producers must follow．AnotherDe—partment controls the foods andDrugs that companiessell．A thirdDepartment looks at theplaces where people work，and then reports any companies that are breaking laws which protectthe health and safety of workers．Of course，new governmentDepartments and new laws cannotprevent every accident or illness，but they are having some good results．Our work places aresafer and cleaner than before．The planes and cars which we use for travel are better．Producersare thinking more about the safety and health of the people who buy and use their products
The main topic of the passage is_________． A．conditions in the work place
B．the freedom of industries in the past
C．changes in industrial production
D．the safety and health of workers and customers
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