The pattern in this sequence is as follows:

Of the three letters the first is the third next letter in the alphabetical sequence of the first letter in the previous term.

The second letter is the second next letter in the alphabetical sequence of the second letter in the previous term.

Similarly the third letter is the 5th next letter in the alphabetical sequence of the third letter in the previous term.

Let's find the second term from the first term.

JWM: _ _ _

Third letter after J is M

Second letter after W is Y.

Fifth letter after M is R.

So, the second term is MYR.

In the same way, the next term of SCB is 

Third letter after S is V

Second letter after C is E.

Fifth letter after B is G.

VEG is the correct answer.