One effect of setting the value of MIRRTEXT=0 is that?

If the MIRRTEXT is set to0 the text is Mirrored with the same image. If the value is set to1 it is reversed. so the option - A is correct. 

answer B, I have searched for that years ago.....If you mirror something, the text gets mirrored as well, so set it on1

My answer is option (a) text is displayed but not mirrored

I agree, with the statement form Mr. Ayoub Tartir for the answer for the question above

a) is for the text is displayed but not mirrored

http://autocadtips1.com/2011/03/10/mirror-text/

"Have you ever mirrored text and it was backwards and looked as if it was being seen through the rear-view mirror of your car? Well this is how you fix that.

Change the System Variable MIRRTEXT:

• <0> keeps the text readable after being mirrored
• <1> mirrors the text direction

In the animated picture below, I mirrored text text objects with their respective variable setting and then show that these variable settings do not effect text that is within blocks."