Solution
= Solution
{c}
A map $f:X\to Y$ is <continuous> if the inverse image of every open subset of $Y$ is open in $X$:
$$
V\in\mathcal T_Y\quad\Longrightarrow\quad f^{-1}(V)\in\mathcal T_X.
$$
= Solution
{c}
A map $f:X\to Y$ is <continuous> if the inverse image of every open subset of $Y$ is open in $X$:
$$
V\in\mathcal T_Y\quad\Longrightarrow\quad f^{-1}(V)\in\mathcal T_X.
$$