Are you legal to take off from here?

It's a good guess. You're aligned with the runway, and why waste pavement? But notice the yellow paint. You're still on a taxiway. This is referred to as a taxiway aligned with a runway. It caused too much confusion, and the FAA no longer permits this for new airports, but there are still examples of them in the wild, as in this example at N07. The correct answer is C.

It was a good guess. But displaced thresholds are marked with white paint. The white bar and the white arrowheads are up ahead, past the yellow demarcation bar running across the pavement. The runway begins on the other side of it. The paint under you is yellow, so you're still on a taxiway. The correct answer is C.

Nicely done — you know your airport markings

You're not on the displaced threshold yet. That's still up ahead, past the yellow demarcation bar, marked with the white bar and white arrowheads. And you could take off from a displaced threshold anyway, you just can't land on one. The paint under you is yellow, so you're still on a taxiway. The correct answer is C.