Final answer:
The sentence "I drew an illustration for a poem that was written by Robert Frost" is a declarative sentence.
Step-by-step explanation:
The sentence "I drew an illustration for a poem that was written by Robert Frost" is a declarative sentence. A declarative sentence makes a statement or expresses an opinion. It provides information or expresses a fact, and it ends with a period. In this sentence, the speaker is stating that they created an illustration for a poem written by Robert Frost.