Instruction: In a certain code language, Greek letters are used to represent English letters consistently. Using the provided code, decode the target sequence. If γ α λ α ξ ι α is coded as GALAXIA, σ τ α ρ is coded as STAR, Question: Then what does σ γ α λ α represent?

Correct — A.
Rule: each Greek letter stands for one English letter, the same everywhere.

From GALAXIA: γ = G, α = A, λ = L, ξ = X, ι = I
From STAR: σ = S, τ = T, α = A, ρ = R

σ γ α λ α = S, G, A, L, A = SGALA → option (a).

Why the others are wrong

• (b)
  SPALA — SPALA reads γ as P. In GALAXIA, γ is the first symbol and G the first letter, so γ = G. No symbol in either example stands for P.
• (c)
  SRALA — SRALA reads γ as R. R is coded by ρ, the last symbol of STAR, and the target σ γ α λ α contains no ρ.
• (d)
  SMALA — SMALA puts M second. Neither coded word contains an M, and the second symbol, γ, is G from GALAXIA.

A symbol code is a substitution: each symbol maps to one letter, and the order of the word is kept. Line each coded word up with its English word, symbol by symbol, and write down the pairs.

Then decode the target from that table. Every symbol in σ γ α λ α appears in the two examples, so nothing has to be guessed.

Key facts

• From GALAXIA: γ = G, α = A, λ = L, ξ = X, ι = I.
• From STAR: σ = S, τ = T, ρ = R.
• A substitution code changes the symbols, not the order of the letters.

Common traps

• Decoding by what a symbol looks like instead of from the table: γ resembles a Latin y, but here it codes G
• Reading the target symbols out of order

No directly related past PYQ was found.