Error spotting (exam direction): Identify the erroneous part (A/B/C) — choose D if there is no error — 'My father goes / to the office / five day week. / No error.'

Given parts (A–D)
A. My father goesB. to the officeC. five day week.D. No error.

Concept/Approach (compound adjective + article)
When a numeral modifies a singular noun used attributively, use a hyphenated compound and an article: 'a five-day week'.

Step-by-step correction
1) Insert article and hyphen: 'five day week' → 'a five-day week'.2) Correct sentence: 'My father goes to the office a five-day week.'

Common pitfalls
Omitting the hyphen and article in compound time expressions.

Final Answer
C — write 'a five-day week'.