Which of the following alternatives will replace the question mark? Alpha, Beta, Gamma, Delta, ?

Correct — C.
Rule: the Greek alphabet, in order.

Alpha is the 1st letter, Beta the 2nd, Gamma the 3rd, Delta the 4th.
The 5th letter is Epsilon → option (c).

After it come Zeta (6th), Eta (7th) and Theta (8th).

Why the others are wrong

• (a)
  Sigma — Sigma is the 18th Greek letter, the Greek S. It belongs to the alphabet, but thirteen places past the 5th that the series needs.
• (b)
  Zeta — Zeta is the 6th letter, one place too far. It comes straight after Epsilon, the 5th letter the series needs.
• (d)
  Theta — Theta is the 8th letter. Epsilon, Zeta and Eta all come between Delta and Theta, so it skips three places.

This series has no arithmetic in it. The terms are the names of the Greek letters in alphabetical order, so the answer is simply the next name.

Every option here is a Greek letter, so recognising the name is not enough: you need its position. The first eight are worth knowing in order: alpha, beta, gamma, delta, epsilon, zeta, eta, theta.

Key facts

• The Greek alphabet has 24 letters, from alpha to omega.
• The first eight in order: alpha, beta, gamma, delta, epsilon, zeta, eta, theta.
• Sigma is the 18th letter of the Greek alphabet.

Common traps

• Choosing Zeta by skipping Epsilon, the 5th letter
• Choosing Theta or Sigma because the name is familiar from maths

No directly related past PYQ was found.