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.

The correct option is (b) and (c) only.

Let us analyze each statement step-by-step to determine its correctness:

Statement (a): "Lipids having only single bonds are called unsaturated fatty acids."
This statement is incorrect. Fatty acids with only carbon-carbon single bonds in their hydrocarbon chains are called saturated fatty acids. Unsaturated fatty acids contain one or more carbon-carbon double or triple bonds.

Statement (b): "Lecithin is a phospholipid."
This statement is correct. Lecithin (specifically phosphatidylcholine) is a key phospholipid found in cell membranes, composed of glycerol, two fatty acids, a phosphate group, and a choline group.

Statement (c): "Trihydroxy propane is glycerol."
This statement is correct. Glycerol is a simple polyol compound with the chemical formula $C_3{H}_8{O}_3$. Its systematic IUPAC name is propane-1,2,3-triol, commonly referred to as trihydroxy propane.

Statement (d): "Palmitic acid has 20 carbon atoms including carboxyl carbon."
This statement is incorrect. Palmitic acid is a saturated fatty acid that has 16 carbon atoms in total, including the carboxyl carbon.

Statement (e): "Arachidonic acid has 16 carbon atoms."
This statement is incorrect. Arachidonic acid is a polyunsaturated omega-6 fatty acid that has 20 carbon atoms, including the carboxyl carbon.

Therefore, only statements (b) and (c) are correct, which corresponds to the option (b) and (c) only.