During an Election Rally, the Visiting Presidential Nominee Invited the Mayor

During an election rally, the visiting presidential nominee invited the mayor for a speech. The mayor was not prepared, which resulted in a mediocre speech. What would you call this kind of speaking, and why should it be avoided?

A) Impromptu speaking; it should be avoided because the message may be weak in terms of words or its effectiveness.
B) Extemporaneous speaking; it should be avoided because the message cannot be delivered the same way the next time.
C) Manuscript speaking; it should be avoided because the final presentation may not be conversational.
D) Memorized speaking; it should be avoided because it lacks the security of a script that the speaker can refer to in case of memory block.