The titration curve of weak acid vs. strong base with phenolphthalein as indicator is shown below. The \( K_{\text{phenolphthalein}} = 4 \times 10^{-10} \). [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 \( \mathrm{pH} = 8.4 \).
(C) It is a weak organic base
(D) It is colourless in acidic medium
