Indirect objects are nouns or pronouns that receive the direct object of a verb. They typically answer the question "to whom?" or "for whom?". They are not the primary focus of the verb's action, but rather the recipient of the direct object.
Adverbs modify verbs, adjectives, or other adverbs. They describe how, when, where, or to what extent something is done.
Adjectives modify nouns or pronouns. They describe the quality, quantity, or state of being of the noun or pronoun.
Since indirect objects are not the primary subject or object of a verb, they cannot be modified directly by adverbs or adjectives.
Example:
* Incorrect: "He gave a gift *quickly* to her."
* Correct: "He gave her a gift quickly."
Explanation: "Quickly" modifies the verb "gave" and describes how the gift was given. "Her" is the indirect object and cannot be modified by an adverb.
However, you can modify the noun or pronoun that serves as the indirect object with an adjective:
* Correct: "He gave a gift to *his* sister."
In this case, "his" modifies the noun "sister," which is the indirect object.