We have lived here __________ ten years.

The correct answer is B: for. This question tests your understanding of prepositions used to express duration, specifically 'for' and 'since'. The preposition 'for' is used to indicate a period of time, answering the question "how long?". In the sentence "We have lived here __________ ten years," 'ten years' represents a duration, a length of time that has passed. Therefore, 'for' is the appropriate choice to convey that the action of living has continued over this specific period. For example, "I have studied for three hours." In contrast, 'since' is used to indicate a starting point in time, answering the question "from when?". For instance, "I have lived here since 2010." If the sentence had been "We have lived here __________ 2010," then 'since' would be correct. 'From' and 'at' are not suitable in this context to express duration. Understanding the distinction between 'for' and 'since' is crucial for accurate temporal expressions in English.