R-410A is considered to be non-toxic but: (A) A) is flammable. (B) B) is a Class I refrigerant. (C) C) is lighter than air. (D) D) can cause asphyxia.

R-410A is a widely used refrigerant in HVAC systems and is classified based on its safety characteristics. While it is considered non-toxic, it's important to be aware of its other properties: **(A) Is flammable.** - **Correct.** R-410A is classified as mildly flammable (A2L) under ASHRAE standards. This means that while it has a low level of flammability, precautions should still be taken during its handling and use to prevent any potential fire hazards. **Explanation of Other Options:** - **(B) Is a Class I refrigerant.** - **Incorrect.** Class I refrigerants are typically ozone-depleting substances. R-410A is a hydrofluorocarbon (HFC) and is classified under Class II, which includes non-ozone-depleting refrigerants. - **(C) Is lighter than air.** - **Incorrect.** The components of R-410A are generally slightly heavier than air, which means they can accumulate in low-lying areas in the event of a leak. - **(D) Can cause asphyxia.** - **Partially Correct but Not the Best Answer.** While R-410A can displace oxygen and potentially lead to asphyxiation in high concentrations, this is not its primary safety concern compared to its flammability. Therefore, option (A) is a more accurate and directly relevant answer. **Best Answer:** **(A) is flammable.**