The titration curve of weak acid vs. strong base with phenolphthalein as indicator is shown below. The $$K_{phenolphthalein} = 4 × 10^{−10}$$
Given: $$log  2 = 0.3$$

The number of following statement/s which is/are correct about phenolphthalein is ______
A. It can be used as an indicator for the titration of weak acid with weak base.
B. It begins to change colour at pH = 8.4
C. It is a weak organic base
D. It is colourless in acidic medium