I am having trouble answering a multiple choice question, in this question there can be multiple answers and there are 5 choices.

3a+b+9c-2d=20

7b -8d=2

3a +9c =24

I found b=-26 and d=-23. I am pretty sure that is right, however if you insert that into the first equation you get 3a+9c = 0. However that may be a part of the answer, heres the possible answers.

A. 'c' can be determined uniquely

B. If a=-1, then c=4

C. The solution has three paramaters.

D. The solution has two parameters.

E. 'd' can be expressed in terms of 'a' and 'b' alone.

Remember you can select more than one option. Any insight would be much appreciated.