The exercise below comes from my English textbook:
Decide which answer A, B, C or D best fits each space.
I’m sorry I haven't written to you for so long, but I have been very busy lately. All last month I had exams, and I haven't done anything else but study for ages. Anyway, I have stopped studying now., and I am waiting for my exam results.
As you can see from the letter, I have changed my address and live in Corydon now. I __________ that I wanted a change from central London because it has become so expensive. A friend of mine told me about this flat, and I moved here about two months ago.
When you come to London this summer, please visit me. I am staying here until the middle of August. Then I am going on holiday to Scotland.
Please write soon,
B. have decided
C. was deciding
The given answer key is B (have decided). I think the author uses the present perfect in order to suggest that the decision made in the past is still of importance in the present.
Is it possible for me to choose A (decided) - the simple past tense? If so, is there any difference in the meaning between option A & B in this case?