Error spotting (exam direction): Identify the erroneous part (A/B/C) — choose D if there is no error — 'Troy was taken by Greeks / this formed the basis of a story / which has become famous. / No error.'

Given sentence parts (A–D)
A. Troy was taken by GreeksB. this formed the basis of a storyC. which has become famous.D. No error.

Concept/Approach (article use with nationality nouns; sentence linkage)
With nationality nouns referring to a people collectively, use the definite article: 'the Greeks'. Also, two independent clauses (A and B) require proper linkage (e.g., 'and' or a semicolon). The tested error is the article omission in Part A.

Step-by-Step correction
1) Insert article: 'by Greeks' → 'by the Greeks'.2) (Stylistic) Link clauses: 'Troy was taken by the Greeks, and this formed the basis of a story which has become famous.'

Verification/Alternative
Other examples: 'the Romans', 'the French' when denoting a nation as a people.

Common pitfalls
Omitting 'the' with collective nationality nouns; comma splices.

Final Answer
A — 'Troy was taken by Greeks' → 'Troy was taken by the Greeks'.