The given sequence is EJO, TYD, INS, XCH. We need to find the missing element in this sequence.

1. Finding the pattern:
Let's analyze the given sequence to identify any patterns or relationships between the elements.

- The first letter of each element follows the pattern: E, T, I, X.
- The second letter of each element follows the pattern: J, Y, N, C.

2. Analysis of the first letters:
If we look at the first letters of each element (E, T, I, X), we can see that they are in alphabetical order. Therefore, the missing first letter should be the next letter in the alphabetical order after X, which is Y.

3. Analysis of the second letters:
If we look at the second letters of each element (J, Y, N, C), we can see that they are in reverse alphabetical order. Therefore, the missing second letter should be the next letter in the reverse alphabetical order after C, which is B.

4. Putting the missing elements together:
Based on our analysis, the missing element should have the first letter Y and the second letter B.

5. Checking the options:
a) NRW: This option does not match the pattern we identified.
b) MRW: This option matches the pattern we identified. The first letter is Y and the second letter is B.
c) MSX: This option does not match the pattern we identified.
d) NSX: This option does not match the pattern we identified.

6. Conclusion:
After analyzing the given sequence and checking the options, we can conclude that the missing element is MRW. Therefore, the correct answer is option B.