To solve this problem, we need to analyze the given statements about genetically engineered insulin:$\newline \bullet$(a) Pro-hormone insulin contains an extra stretch of C-peptide.$\newline$ - This statement is correct. Pro-hormone insulin, also known as proinsulin, includes the A-chain, B-chain, and C-peptide. The C-peptide is removed to produce mature insulin.$\newline \bullet$(b) A-peptide and B-peptide chains of insulin were produced separately in E. coli, extracted, and combined by creating a disulfide bond between them.$\newline$ - This statement is correct. In the production of genetically engineered insulin, the A and B chains are synthesized separately in E. coli and then chemically combined to form functional insulin.$\newline \bullet$(c) Insulin used for treating diabetes was extracted from cattle and pigs.$\newline$ - This statement is correct. Before the advent of recombinant DNA technology, insulin was extracted from the pancreas of cattle and pigs for medical use.$\newline \bullet$(d) Pro-hormone insulin needs to be processed for converting it into a mature and functional hormone.$\newline$ - This statement is correct. Proinsulin undergoes enzymatic processing to remove the C-peptide, resulting in mature insulin.$\newline \bullet$(e) Some patients develop allergic reactions to the foreign insulin.$\newline$ - This statement is correct. Some patients experienced allergic reactions to animal-derived insulin due to slight differences in the amino acid sequence compared to human insulin.$\newline$Now, let's determine which statements are included in the options:$\newline \bullet$Option 1: (a), (b), and (d) only$\newline \bullet$Option 2: (b) only$\newline \bullet$Option 3: (c) and (d) only$\newline \bullet$Option 4: (c), (d), and (e) only$\newline$The correct option is Option 2, as it includes only statement (b), which is a key aspect of genetically engineered insulin production.