We know, `P(X)` should be between `0 and 1`.
Also, sum of all the probablities in a probablity distribution should be 1.
(i) Here, sum of all probablities is 1 and all probablities are between 0 and 1.
So, this is a probablity distribution.
(ii) Here, P(X=3) is negative. So, this is not a probablity distribution.
(iii) Here, sum of all probablities is `0.9` which is less than 1.So, this is not a probablity distribution.
(iv)Here, sum of all probablities is `1.05` which is greater than 1.So, this is not a probablity distribution.