Each series is made up of increasing consecutive letters. The construction of the series follows a pattern where each letter is two places ahead of the previous one. For example, `P` is followed by `Q` which is one letter ahead and `O` is sandwiched between them. In similar pattern, `S` is followed by `T` and `R` is in between them, and `V` is followed by `W` with `U` in between. Following this pattern, after `V`, `W`, `X` should come, then `Y` and between `X` and `Y`, `Z` should be sandwiched. Hence, the correct answer is `YXZ` (option 3) and not others. Option 1, 2 and 4 are incorrect as they do not follow the pattern of the given series.