In which of the following sentences is the word 'after' used as a preposition ?
(a) They arrived after us.
(b) They arrived after we had left.
(c) I went for a short walk after dinner.
(d) After he finished his studies, he went to America.

Question

In which of the following sentences is the word 'after' used as a preposition ?
(a) They arrived after us.
(b) They arrived after we had left.
(c) I went for a short walk after dinner.
(d) After he finished his studies, he went to America.

Accepted Answer

Option 3 is the correct answer because it identifies the sentences where the word 'after' is used as a preposition. Let's analyze each sentence to understand why this is the case:

1. **Sentence (a): "They arrived after us."**
   - In this sentence, 'after' is used as a preposition. It shows the relationship between 'they arrived' and 'us,' indicating the sequence of events. The word 'us' is the object of the preposition 'after.'

2. **Sentence (b): "They arrived after we had left."**
   - In this sentence, 'after' is used as a conjunction, not a preposition. It connects two clauses: 'They arrived' and 'we had left.' Therefore, it does not fit the criteria for 'after' being used as a preposition.

3. **Sentence (c): "I went for a short walk after dinner."**
   - Here, 'after' is used as a preposition. It indicates the relationship between 'I went for a short walk' and 'dinner,' specifying the time sequence. 'Dinner' is the object of the preposition 'after.'

4. **Sentence (d): "After he finished his studies, he went to America."**
   - In this sentence, 'after' is used as a conjunction. It connects the clause 'he finished his studies' with 'he went to America.' Thus, it is not used as a preposition here.

Now, let's explain why the other options are incorrect:

- **Option 1: Only (a)**
  - This option is incorrect because it only identifies sentence (a) as using 'after' as a preposition, missing sentence (c), which also uses 'after' as a preposition.

- **Option 2: (a) and (b)**
  - This option is incorrect because it includes sentence (b), where 'after' is used as a conjunction, not a preposition.

- **Option 4: (b) and (d)**
  - This option is incorrect because both sentences (b) and (d) use 'after' as a conjunction, not as a preposition.

Therefore, Option 3 is the correct answer as it accurately identifies sentences (a) and (c) where 'after' is used as a preposition.