i need help with part a and b, not sure if they are or are not linear or not,

for part c) can i set x = 0 and y = , which gives me 2, which does not equal 0, so part c is not a linear map?

also part d, is not a linear map because if a =0 , b = 0, and c= 0, than we get 0, in the transformation T, so it is a linear map ?

Thank you.