Enzyme Cleaves NP-P Bonds, Isolating Singles Steps:

• Examine the diagram's sequence of amino acids marked as polar basic (■), polar acidic (○), or non-polar (▭).
• Identify all peptide bonds between non-polar (▭) and any polar (■ or ○) amino acids for hydrolysis.
• Hydrolysis breaks the chain into fragments of consecutive same-type amino acids.
• Count fragments of length 1 (single amino acids) released as monomers.

Why D is correct:

• The sequence has 4 isolated amino acids (each flanked by opposite types), yielding 4 singles after all 13-1=12 possible bonds are selectively cleaved where NP meets polar.

Why the others are wrong:

• A: Counts only 1 single, ignoring 3 more isolated polars.
• B: Identifies 3 singles but misses the 4th non-polar isolate.
• C: Tallies 3 singles, confusing adjacent same-types as separate.

Final answer: D