Misc: In 1945 Bjorn ---------- , rock vocalist/guitarist (ABBA), born.?

Questions

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

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 ?