The correct answer is C. has been making/has finished.
Mrs. White started making the dress in November, and she has been working on it ever since. She has finished most of the dress, except for the trimmings. This means that she has been working on the dress for a long time, and she is almost done.
The other options are not correct because they do not accurately describe the situation. Option A, made/finished, is not correct because Mrs. White is still working on the dress. Option B, was making/was finishing, is not correct because Mrs. White is no longer in the process of finishing the dress. Option D, is making/finished, is not correct because Mrs. White has not finished the dress. Option E, makes/is finishing, is not correct because Mrs. White is not currently making the dress.
In conclusion, the correct answer is C. has been making/has finished.