十七、閱讀下列英文，回答問題：

      Organic solvents are classified into three categories based on their toxicity to humans, volatility, and carcinogenicity (致癌性)：

      The type 1 (highest toxicity)：These are mostly halogenated hydrocarbons (such as chloroform and tetrachloroethylene), carbon disulfide, etc. These are extremely toxic to humans and can easily cause neurotoxicity (神經毒性), peripheral neuropathy (周邊神經病變), or carcinogenic risks(致癌風險).

     The second type of organic solvent (moderate toxicity): These include common industrial solvents such as n-hexane, cyclohexane, acetone, benzene, toluene, xylene, ethyl acetate, etc. Longterm exposure can cause neurotoxicity and numbness in the limbs (四肢麻木).

    The third type of organic solvent (lowest toxicity): These are mainly alcohols (such as methanol and ethanol) and ethers (such as diethyl ether), which are relatively less toxic than the first two types, but still have volatility and flammability risks.

    In the human body, n-hexane is metabolized (代謝) by the liver to produce the neurotoxic metabolite 2,5-hexanedione. This metabolite 2,5-hexanedione reacts with lysine residues in axonal proteins (軸突蛋白) of nerve cells, hindering nerve cell metabolism, and leading to peripheral neuropathy. Using n-heptane instead of n-hexane can effectively reduce the risk of poisoning. The main hazard of n-hexane lies in its metabolites, which can cause peripheral neuropathy; while nheptane does not possess this strong peripheral neurotoxicity and has lower toxicity, making it a commonly used "alternative" friendly solvent in occupational health. However, n-heptane is still irritating, flammable and highly volatile, and should be used in well-ventilated areas and away from sources of ignition.