🔍 Key Concepts

• Physical properties of castor oil such as specific gravity and boiling point • Difference between vapor pressure of volatile fuels and non‑volatile oils • USCG/49 CFR definitions of flammable vs. combustible liquids and letter grades (A–E)

💭 Think About

• Compare each numerical property (specific gravity, boiling point, vapor pressure) with what you would generally expect for a heavy, non‑volatile vegetable oil. • Think about whether castor oil behaves more like gasoline/jet fuel or like cooking oil when it comes to evaporation and ignition. • Recall how combustible liquid grades are assigned (by flash point range) and decide which grade, if any, best matches castor oil’s typical flash point.

✅ Before You Answer

• For each choice, ask: Does this sound like a highly volatile substance or a heavy, oily liquid? • Verify the typical range of specific gravity for vegetable oils versus water (1.0) to judge option A. • Review the definition of combustible liquid grades and what approximate flash point range corresponds to grade E before deciding on option D.