the ones that simplify to x=x or c=c where c is a constant
as soon as you have
ax+b=c where a, b, and c are constants (and b≠0 and a≠0), then there is one solution
A. -4.4+3y=4.3-3y
-4.4+6y=4.3
this has one solution
B. -1/3y+2.5=1.2
this has 1 solution
C.
6.3+2y=6.3+2y
2y=2y
y=y
infinite solutions
D. 4/10y=2.3+15/10y
-11/10y=2.3
1 solution
C is the answer