Given that A=B and B=C.
By the transitive property of equality, if two quantities are each equal to a third quantity, then they are equal to each other.
Since A=B and B=C:
A=C
Examining the other options:
Option 2: If A+B=C and A=B, this would give B+B=C or 2B=C, which contradicts B=C.
Option 3: A=B directly contradicts the given condition A=B.
Option 4: B=C directly contradicts the given condition B=C.
Therefore, the correct answer is Option 1: A is equal to C.