Given a scientific passage and an answer, generate a question for the given answer.
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Question: Passage: When there is no mass in a volume of space, the space is not curved. An object passing through such space would follow a straight line in our normal way of thinking of a straight line. Answer: curved

Answer: When there is no mass in a volume of space, the space is not what?

Question: Passage: Benzoic acid crystals in polarized light are pictured above. Benzoic acid is widely used as a food preservative, either as the carboxylic acid or as the sodium benzoate salt. This compound is most effective when added to acidic foods such as fruit juices and soft drinks. The major industrial source of benzoic acid is the partial oxidation of toluene with oxygen. The process is inexpensive and environmentally benign. Answer: benzoic acid

Answer: What type of acid is often used as a preservative for acidic foods such as fruit juices?

Question: Passage: Bacteria that cause foodborne illnesses include Salmonella , a bacterium found in many foods, including raw and undercooked meat, poultry, dairy products, and seafood. Campylobacter jejuni is found in raw or undercooked chicken and unpasteurized milk. Several strains of E. coli can cause illnesses, and are found in raw or undercooked hamburger, unpasteurized fruit juices and milk, and even fresh produce. Vibrio is a bacterium that may contaminate fish or shellfish. Listeria has been found in raw and undercooked meats, unpasteurized milk, soft cheeses, and ready-to-eat deli meats and hot dogs. Most of these bacterial illnesses can be prevented with proper cooking of food and washing of hands. Answer: hands

Answer:
Most of these bacterial illnesses can be prevented with proper cooking of food and washing what?