Which one of the following structures represents the peptide chain [CBSE PMT 2004; CPMT 2003; DCE 2002; MP PET 1994; Bihar MEE 1997; Orissa JEE 1997]

• A.                 \[-\overset{H}{\mathop{\overset{|}{\mathop{N}}\,}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\underset{O}{\mathop{\underset{||}{\mathop{C}}\,}}\,-\overset{H}{\mathop{\overset{|}{\mathop{N}}\,}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\underset{O}{\mathop{\underset{||}{\mathop{C}}\,}}\,-\overset{H}{\mathop{\overset{|}{\mathop{N}}\,}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\overset{O}{\mathop{\overset{||}{\mathop{C}}\,}}\,-\]
• B.                 \[-\overset{H}{\mathop{\overset{|}{\mathop{N}}\,}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\overset{O}{\mathop{\overset{||}{\mathop{C}}\,}}\,-\underset{H}{\mathop{\underset{|}{\mathop{N}}\,}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\overset{H}{\mathop{\overset{|}{\mathop{N}}\,}}\,-\underset{O}{\mathop{\underset{||}{\mathop{C}}\,}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\]
• C.                 \[-\overset{H}{\mathop{\overset{|}{\mathop{N}}\,}}\,-\underset{O}{\mathop{\underset{||}{\mathop{C}}\,}}\,-\underset{H}{\mathop{\underset{|}{\mathop{N}}\,}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-NH-\overset{O}{\mathop{\overset{||}{\mathop{C}}\,}}\,-NH-\]
• D.                 \[-\overset{H}{\mathop{\overset{|}{\mathop{N}}\,}}\,-\underset{O}{\mathop{\underset{||}{\mathop{C}}\,}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\overset{H}{\mathop{\overset{|}{\mathop{N}}\,}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\underset{|}{\overset{|}{\mathop{C}}}\,-\]