Q88 C and D cannot both be selected

[mharr]

Hi,

I chose the incorrect answer which is D -> ~C. I thought that C and D must be forever apart so I chose the incorrect answer because the negation is on the necessary condition. I have been under the impression that when the negation is on the sufficient condition it is possible for both variables to be selected.

I am confused now because the correct answer is ~C -> D. But doesn't the negation on C (the sufficient condition) make it possible for both C and D to be selected? Which would violate the above rule that C and D cannot both be selected?

Any help would be appreciated.

[christine.defenbaugh]

Hi,

I chose the incorrect answer which is D -> ~C. I thought that C and D must be forever apart so I chose the incorrect answer because the negation is on the necessary condition. I have been under the impression that when the negation is on the sufficient condition it is possible for both variables to be selected.

I am confused now because the correct answer is ~C -> D. But doesn't the negation on C (the sufficient condition) make it possible for both C and D to be selected? Which would violate the above rule that C and D cannot both be selected?

Any help would be appreciated.

You are totally correct that given the rule "C and D cannot both be selected", the correct notations would be:

C --> ~D
D --> ~C

Having one of the elements would mean we couldn't then have the other. Great job on the analysis!

The database shows D -> ~C as the correct answer. You may have been the victim of a mischievous passing data sprite!