ERROR SPOTTING — Identify the part (A–E) that contains a grammatical, usage, or spelling error. Choose the erroneous fragment; if none, choose E. Sentence (split into parts): A) Justice is an enforceable B) public virtue, stronger in C) obligatory than such private virtues as friendship D) charity and E) generosity.

Introduction / Context:
The sentence attempts a comparative construction “stronger in … than …” and contrasts public virtue with private virtues. The error concerns the word form after the preposition “in”.

Given Data / Assumptions:

• Pattern: “stronger in X than Y”.
• Segment C uses “obligatory” (adjective) after “in”.
• Intended meaning: justice is stronger in obligation (or more obligatory) than private virtues such as friendship, charity, and generosity.

Concept / Approach:
After the preposition “in”, a noun should follow. The correct noun is “obligation”. Alternatively, we could recast the comparative as “more obligatory than” (adjective + than). Mixing “in” with an adjective (“obligatory”) is ungrammatical.

Step-by-Step Solution:
1) Identify comparative frame: “stronger in … than …”.2) Supply noun after “in”: “obligation”.3) Rebuild: “Justice is an enforceable public virtue, stronger in obligation than such private virtues as friendship, charity, and generosity.”4) Alternatively: “Justice is more obligatory than such private virtues as friendship, charity, and generosity.”

Verification / Alternative check:
Grammar test: replace “in + adjective” with “in + noun” or remove “in” and keep the adjective with “more … than”.

Why Other Options Are Wrong:
A) Correct start and article usage.B) Comparative lead-in is fine.D–E) Items in a list; punctuation could be improved but not a test error.

Common Pitfalls:
Confusing part of speech after prepositions; prepositions are typically followed by nouns or gerunds.

Final Answer:
C (Replace “obligatory” with “obligation” or recast as “more obligatory than”)