Effective speakers use an extemporaneous delivery, which means the speakers have practiced their speech ahead of time and delivered the actual speech A. from memory B. by reading from a prepared manuscript C. from a speaking outline D. all of the above

B. by reading from a prepared manuscript.

Explanation:

In the manner of speech delivery, there are certain methods that a speaker may employ to successfully give his intended speech. Good speech delivery depends on many factors, which may or may not require the use of cards or pre-written cards. But amidst all these, an extemporaneous speaker may be termed as someone who uses prepared cards to efficiently deliver his speech, which is to say, may not be devoid of any glitches. But the use of the cards will enable the speaker to refer to it anytime he / she gets stuck midway.

So, an effective speaker who uses an extemporaneous delivery is someone who reads from a prepared manuscript.