Choose the incorrect homonym pair:

The correct answer is Option (3) → Access-Excess

Homophones (a kind of homonym) are words that sound the same but differ in spelling and meaning. Access and excess do not sound the same: access begins with an "ak" sound and is stressed on the first syllable, while excess begins with an "ek" or "ik" sound and is usually stressed on the second syllable. So this pair is not a homonym pair.

• Access means the right or way to enter or use something.
  Example: Only staff have access to this room.
• Excess means more than is needed or allowed.
  Example: He paid a fine for carrying excess baggage.

Why the Other Options are Incorrect?

Option 1: Bale-Bail — Incorrect. Correct use: the two words sound the same: a bale is a large bundle (of cotton or hay); bail is money paid to free an accused person until trial.
Example: The court granted him bail.

Option 2: Caste-Cast — Incorrect. Correct use: they sound the same: caste is a social group one is born into; cast means to throw, or the actors in a play.
Example: The film has a talented cast.

Option 4: Ail-Ale — Incorrect. Correct use: they sound the same: to ail is to be ill or to trouble someone; ale is a kind of beer.
Example: What ails the old man?