Gresil: it seems to me that it indeed is a threat: if black ignores , he'll run out of liberties before being able to connect:
unkx80: Oops, your attempt is not quite right. Please try again.
Let's try to solve this by the brute-force method...
After , white is in atari. If white connects at a, black plays at c and connects. If white plays anywhere else, black captures two stones at a and connects. And if is played anywhere else, black will play at and connect.
This transposes to case 1. As stated above, black connects.