Grammar – identify which of the following sentences is grammatically correct.

Introduction / Context:
This multiple choice item tests your understanding of English verb tenses and their correct use with time expressions. Only one of the sentences follows standard grammar and natural usage. You must check how each tense (present perfect, past perfect, present continuous, and simple present or future forms) interacts with specific time markers such as last night and yesterday.

Given Data / Assumptions:

Each option contains a common tense pattern that learners often misuse.
Time expressions like last night and yesterday typically require the simple past rather than present perfect or past perfect in standard British and exam level English.
We assume that the sentences are independent statements, not parts of a larger narrative that could justify unusual tense choices.

Concept / Approach:
The main concepts here are correct pairing of tense with time expressions and understanding of aspect. Present perfect (has or have plus past participle) is used for actions with present relevance without a finished time marker. Past perfect (had plus past participle) describes an action completed before another past action. Present continuous (is plus verb plus ing) describes an action happening now or around the present moment, not a finished duration in the past. The one sentence that avoids conflicts between tense and time expression will be the correct choice.

Step-by-Step Solution:
Step 1: Option A We had gone to the party last night mixes past perfect with the finished time expression last night. Usually we use simple past for a single finished event at a known time, for example We went to the party last night. Step 2: Option B I have seen him yesterday is incorrect because present perfect is normally not used with specific past time expressions like yesterday; the correct form would be I saw him yesterday. Step 3: Option C The hen has laid ten eggs uses present perfect to describe a result that is relevant now. There is no specific finished time mentioned, so present perfect is appropriate and fully grammatical. Step 4: Option D She is sleeping for two hours is wrong because present continuous with for plus duration is not used to describe a completed period. For a period continuing up to now we would say She has been sleeping for two hours. Step 5: Option E We are going to the party last night mixes a present progressive form with a past time marker, which is clearly inconsistent.

Verification / Alternative check:
To double check, rewrite each sentence in standard form. For A, the natural sentence is We went to the party last night. For B, the natural sentence is I saw him yesterday. For D, correct grammar would be She has been sleeping for two hours if the action started in the past and continues now. For E, a correct version for present time would be We are going to the party tonight, not last night. These rewrites confirm that only C is already correctly formed and does not require any change.

Why Other Options Are Wrong:
Option A misuses past perfect, which should be reserved for sequences such as We had gone to the party before it started raining, where one past action precedes another.
Option B joins present perfect with a clear past time marker, which standard exam grammar teaches as incorrect usage.
Option D uses present continuous to describe a duration that is better handled by present perfect continuous when referring to time up to now.
Option E mixes a present progressive verb with a past time phrase, which conflicts with the basic rule that the tense should match the time reference.

Common Pitfalls:
Learners often overuse perfect tenses because they sound advanced or formal. Remember that simple past is the normal choice with clear completed time expressions such as yesterday, last year, and in 2010. The present perfect is more suitable for experiences (I have visited Delhi) or recent results without a specific time (The hen has laid ten eggs). Practising these common patterns will help you recognise the only fully correct sentence quickly in exam settings.

Final Answer:
The only grammatically correct sentence as written is The hen has laid ten eggs.