Following are the statements with reference to 'lipids'.

(a) Lipids having only single bonds are called unsaturated fatty acids.

(b) Lecithin is a phospholipid.

(c) Trihydroxy propane is glycerol.

(d) Palmitic acid has 20 carbon atoms including carboxyl carbon.

(e) Arachidonic acid has 16 carbon atoms.

Choose the correct answer from the options given below.

To decide which statements about lipids are correct, evaluate each one individually.

(a) “Lipids having only single bonds are called unsaturated fatty acids.”
A fatty acid that contains only single bonds in its hydrocarbon chain is **saturated**, not unsaturated. Unsaturated fatty acids have one or more double (or triple) bonds. Therefore statement (a) is false.

(b) “Lecithin is a phospholipid.”
Lecithin is a common name for phosphatidylcholine, which belongs to the phospholipid class. Phospholipids consist of a glycerol backbone, two fatty‑acid tails, and a phosphate‑containing head group. Hence statement (b) is true.

(c) “Trihydroxy propane is glycerol.”
The chemical name “trihydroxy propane” describes a three‑carbon chain (propane) with three hydroxyl (–OH) groups, exactly the structure of glycerol (HO‑CH₂‑CH(OH)‑CH₂‑OH). Thus statement (c) is true.

(d) “Palmitic acid has 20 carbon atoms including carboxyl carbon.”
Palmitic acid is a saturated fatty acid with the formula C₁₆H₃₂O₂. It contains 16 carbon atoms in total, not 20. Therefore statement (d) is false.

(e) “Arachidonic acid has 16 carbon atoms.”
Arachidonic acid is a polyunsaturated fatty acid with the formula C₂₀H₃₂O₂. It possesses 20 carbon atoms, not 16, making statement (e) false.

Summarizing the evaluations, only statements (b) and (c) are correct. Hence the correct choice is (b) and (c) only.