What makes a good informative speech? An emotional quality
A strong argument
A well-written speech which presents facts
A persuasive speaker

All seem like great qualities, but I truly believe the best answer to this question is:

C) A well-written speech which presents facts

Explanation:

It's best that a speech is well written and grammatically correct. To make it easier for your audience to understand, use words and phrases suitable. For example, if you are a mayor, use professional vocabulary for the topic of the speech. On the other hand, if you are a preschool teacher teaching a class, still be somewhat professional, while also using words younger children (ages 2-6) will be able to understand (and it wouldn't hurt to be entertaining and bubbly so they won't get bored). Also, you want to be sure your speech contains 100% facts. You can do strong research on the topic you will be covering or speak to an expert who knows about it.

the italian poet francesco petrarch did! (: