Which of the following graphs have Euler circuits or Euler trails?

$$ A: Has Euler trail.

${}_{B\text{:}\text{H}\text{a}\text{s}\text{E}\text{u}\text{l}\text{e}\text{r}\text{t}\text{r}\text{a}\text{i}\text{l}\text{.}}$

$$ A: Has Euler circuit.

$$ B: Has Euler circuit.

C: Has Euler trail.

D: Has Euler trail.

$$ C: Has Euler circuit.

$$ D: Has Euler circuit.