Correct Answer: d, e, f, g

Solution : Given:
ac _ bd _ ce _df _ egh

To fill the series we have to divide the series→ac _ / bd _ / ce _ / df _ / egh
Let's check each option –
First option: d, f, g, e; ac d / bd f / ce g / df e / egh. (No repeated pattern has been found.)
Second option: b, d, c, a; ac b / bd d / ce c / df a / egh (No repeated pattern has been found.)
Third option: d, g, f, e; ac d / bdg / ce f / df e / egh (No repeated pattern has been found.)
Fourth option: d, e, f, g; ac d / bd e / ce f / df g / egh (Here, 1 is added in the positional value of the first, second, and third letter of each term.)

So, the series is→acdbdecefdfgegh. Hence, the fourth option is correct.