In an effective speech the
a. spends little time developing the topic
b. clearly introduces the topic
c. states main ideas but does not support them with details
d. allows the listener to come up with his or her own conclusion

Explanation:

In an effective speech the speaker clearly introduces the topic

[ Spends little time developing the topic ] This answer is incorrect.

In order to ensure a clear and strong speech, taking time to develop and create a valid topic is vital. This ensures that the audience will understand and clearly follow your speech. The topic also provides the barriers and grounds for your speech.

[ States main ideas but does not support them with details ] Evidence and details are needed in ensuring a valid speech. Main ideas are just ideas to the wind without backup, evidence and details. Main ideas hook to the topic, but details hook to the main idea.

[ Allows the listener to come up with his or her own conclusion ] This is not a debate. When giving a speech, this is your time, and when it is your time this is when you give your ideas and your topic. Sometimes you can engage with your audience, but you are not to allow them to give your speech for you.  

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explanation: