Misc: What is the fear of definite plans known as?

Questions

The works of Schubert are usually identified by "D" and a number. What does "D" stand for ?

Each movement of Vaughan William's Sinfonia Antarctica contains quotes from the journals of which explorer ?

Who did Herbert Von Karajan replace as conductor of the Berlin Philharmonic ?

What is the Heiligenstadt Testament ?

Mozart, Haydn and Beethoven are sometimes collectively refered to as... ?