Now, I'm not sure what you mean exactly by like terms, but I'll just tell you what I think abouth the equations...
Answer:
A. x times y and x plus y
Now, these are different equations, b/c one is multiplying and the other is adding
B. -8a and a
The first is -8 times a, and the second is just a
C. a times two and two times a
These are exactly the sam equation, just flipped around
D. c times d and d times c
These are exactly the same equation, just flipped around
