If BRICK is coded as CSJDL, how is CSJDL coded?

Correct — A.
Rule: every letter moves +1: B→C, R→S, I→J, C→D, K→L.

Apply the same code to CSJDL:
C→D, S→T, J→K, D→E, L→M

That spells DTKEM → option (a).

Why the others are wrong

• (b)
  DSKEL — DSKEL leaves S and L as they are. The code moves every letter one place, so S must become T and L must become M.
• (c)
  DTKFL — DTKFL moves D two places to F and leaves L unmoved. The rule is +1 at every position: D→E and L→M.
• (d)
  CSKDL — CSKDL shifts only J→K and copies C, S, D and L unchanged. A +1 code moves all five letters.

A code-it-again item applies the same rule twice. Find the rule from the sample pair, then run it on the coded word exactly as you would on a fresh one.

Here the rule is a uniform +1, so coding twice is +2 on the original word: B→D, R→T, I→K, C→E, K→M gives DTKEM. That is an instant check.

Watch the end of the alphabet: under +1, Z wraps round to A.

Key facts

• BRICK → CSJDL moves every letter +1.
• CSJDL → DTKEM moves every letter +1 again.
• Two +1 steps equal one +2 step: BRICK moved +2 is DTKEM.

Common traps

• Shifting only some letters and copying the rest, as in CSKDL.
• Decoding (−1) instead of coding again (+1), which would return BRICK.

No directly related past PYQ was found.