複選題15. Suppose we want to generate randomly 8 bits, with O or 1 in cach bit. Let E1, be the event of bit O being 1, Ez be the event of bit 7 being 0, and Es be the event of both bits 3 and 4 being 1. Which of the following are true? (A) The probability P(E1| E2)= ； (B) The probability P(E1| E2) = ； (C) The probability P(E1| E2, E3)= ；(D) The probability PE2| E1, E3)=