Sort the following events to reflect the order in which they occur for formation of new blood capillaries in conditions of insufficient oxygen supply. Your answer would be a four-letter string composed of letters A to D only, e.g. DACB.
(A) New tip cells are formed on the sides of nearby capillaries.
(B) Stalk cells divide and hollow out to form tubes.
(C) VEGF is secreted by the cell.
(D) The level of intracellular HIF1? increases.