Fill in the missing letter based on an alphabetical pattern. A, C, E, ?, I

Correct — B.
Rule: +2 at every step (skip one letter).

A(1) + 2 = C(3)
C(3) + 2 = E(5)
E(5) + 2 = G(7)
G(7) + 2 = I(9), the given last term → option (b).

Why the others are wrong

• (a)
  F — F(6) is E + 1. The series steps by 2, and F would leave a gap of 3 to I.
• (c)
  H — H(8) is E + 3, which breaks the +2 step, and H to I is a gap of just 1.
• (d)
  J — J(10) comes after I, not before it. The blank sits between E(5) and I(9), and +2 from E gives G.

An alphabet series with a blank in the middle can be checked from both sides. Find the step from the letters before the blank, then make sure your letter also reaches the letter after it.

A, C, E are positions 1, 3, 5, a step of +2. The blank is 7, which is G, and G + 2 lands on I, the given fifth term.

Key facts

• A, C, E, G, I are positions 1, 3, 5, 7, 9.
• A middle blank must fit the step on both sides: E + 2 = G and G + 2 = I.

Common traps

• Choosing F because it follows E, without checking the gap to I
• Treating the blank as the next term and choosing J

No directly related past PYQ was found.