Error spotting (exam direction): Identify the erroneous part (A/B/C) in the sentence — choose D if there is no error — 'Many health-conscious people / prefer margarine / than butter. / No error.'

Given sentence parts (A–D)
A. Many health-conscious peopleB. prefer margarineC. than butter.D. No error.

Concept/Approach (verb + preposition pattern)
The verb 'prefer' takes the preposition 'to', not 'than': 'prefer X to Y'.

Step-by-Step correction
1) Locate collocation: 'prefer margarine than butter'.2) Replace 'than' → 'to': 'prefer margarine to butter'.3) Correct sentence: 'Many health-conscious people prefer margarine to butter.'

Verification/Alternative
Other correct forms: 'would rather eat margarine than butter' (note the different structure).

Common pitfalls
Using 'than' after 'prefer' due to confusion with comparative constructions.

Final Answer
C — 'than butter.' should be 'to butter.'