1. Because the last bus had gone, we had to walk home.

2. Because the last bus went, we had to walk home.
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Which one is correct?

Both sentences are grammatically correct, but there is a slight difference in meaning between them.

1. "Because the last bus had gone, we had to walk home."

In this sentence, we are using the past perfect tense ("had gone") to describe an event that happened before another past event. The action of the bus leaving (going) happened before the action of us having to walk home. This sentence implies that when we reached the bus stop, the bus was already gone, and as a result, we had no choice but to walk home.

2. "Because the last bus went, we had to walk home."

In this sentence, we are using the simple past tense ("went") to describe an event that happened in the past. The action of the bus going happened, and as a result, we had to walk home. This sentence implies that we missed the bus, and it resulted in us having to walk home.

So, both sentences are correct, but they convey slightly different meanings. Sentence 1 emphasizes the completion of the bus leaving before we started walking home, while sentence 2 emphasizes the act of the bus going, which caused us to walk home.