Step 1: Interpreting the meaning of the two sentences.
The first sentence states that Tanya is extremely polite.
The second sentence states that we like her.
The relationship between the two sentences shows a cause-and-effect connection.
Step 2: Evaluating the options.
(A) uses but, which shows contrast. There is no contrast in the original sentences.
(B) uses despite, which also shows contrast and alters the intended meaning.
(C) is grammatically acceptable but slightly alters the structure and emphasis of the original sentence.
(D) correctly combines both sentences using because, clearly showing that we like Tanya due to her politeness.
Step 3: Final Conclusion.
Hence, the correct combined sentence is option (D), as it logically and grammatically connects the cause and effect.