firstly, the negative sign indictaes that this is a decay. Secondly, it
is decaying by 31% (or 31 per 100) per annum, or 0.31, however, I dont
think any of these answers are right.
certainly C and D represent growth as they are 131% and 169% (1.31 and
1.69 respectively), B represents a decrease of 4% or 0.04, and A
represents a decrease of 87% or 0.87, which as you can see does not
correspond to to a decrease of -0.31or -31%, are you sure you have
supplied all the information in the question(such as a starting point).
If you have then I would refer to teacher/tutor for further examination.
