Which sentence uses an objective case pronoun as an indirect object?

i e-mailed him yesterday.
i sent him an attachment that included photos of the picnic.
he wrote back to bob and i with an answer to our questions.

Which sentence uses an objective case pronoun as an indirect object?

I sent him an attachment that included photos of the picnic.

The indirect object him identifies to whom the action of the verb sent is performed.  

Wrong options:

I e-mailed him yesterday.

(The direct object him is the receiver of action within this sentence: I emailed him).

He wrote back to Bob and I with an answer to our questions.

(I is not an objective case pronoun; it should be "He wrote back to Bob and me...")

So, once again, the answer is the 2nd sentence (I sent him an attachment that included photos of the picnic.)

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