Computer-Assisted Presentations Have Which of the Following Drawbacks

Computer-assisted presentations have which of the following drawbacks?

A) They can be very time-consuming to prepare.
B) Glitches may occur that could be a disaster if the speech is largely dependent on computer assistance.
C) They can diminish the speech content's effectiveness when no computer "bells and whistles" are available for certain parts of the presentation.
D) They require more practice than traditional visual aids.