He pulled ____ boy by ____ ear.

The correct sentence is:

"He pulled the boy by the ear."

Explanation:

• "a, a" implies any boy and any ear, which is too vague for the context where a specific boy and his specific ear are involved.

• "a, an" has the same issue as "a, a," lacking specificity.

• "the, the" is correct as it specifies a particular boy and his ear, making the action and subjects definite and specific.

• "an, a" is grammatically incorrect due to the misuse of "an" before "boy," which doesn't start with a vowel sound, and "a" before "ear," which starts with a vowel sound and should be preceded by "an" in an indefinite context.