- A$P$ (only one of them occurs)
$ = P({\bar E_1}{E_2}{E_3} + {E_1}{\bar E_2}{E_3} + {E_1}{E_2}{\overline E _3})$
- B$P$ (none of them occurs)
$ = P({\overline E _1} + {\overline E _2} + {\overline E _3})$
- ✓$P$ (atleast one of them occurs)
$ = P({E_1} + {E_2} + {E_3})$
- D$P$ (all the three occurs)$ = P({E_1} + {E_2} + {E_3})$
where $P({E_1})$denotes the probability of ${E_1}$ and ${\bar E_1}$ denotes complement of ${E_1}$.