Which of the following substances is considered safe and not classified as flammable or corrosive?

Anhydrous citric acid is considered safe and is not classified as flammable or corrosive. It is commonly used as a food additive and a natural preservative due to its ability to act as a natural acidifier. In its dry form, it is stable and does not pose the same risks as many chemical substances that can ignite or cause chemical burns.

In contrast, sulfuric acid is highly corrosive and can cause severe burns upon contact with skin or eyes. It is also a strong dehydrating agent and can react violently with water. Acyclic hydrocarbons, such as alkanes, are flammable and can pose risks of fire and explosion in certain conditions. Chlorine gas, while useful for disinfection and water treatment, is toxic and can cause respiratory issues; it is also considered corrosive to tissues. Therefore, anhydrous citric acid stands out as the safe choice among the given substances.