Puzzling

This is puzzling.

I can see how that would be puzzling.

This is quite puzzling.

I find this puzzling.

Korean is a puzzling language to learn, isn't it?

It's very puzzling.

I've been puzzling over it.

It was puzzling to me.

It's so puzzling.

His behaviour was puzzling to me.

Sunning himself on the board steps, I saw for the first time Mr. Farquhar Fenelon Cooke.[…]A silver snaffle on a heavy leather watch guard which connected the pockets of his corduroy waistcoat, together with a huge gold stirrup in his Ascot tie, sufficiently proclaimed his tastes.[…]But withal there was a perceptible acumen about the man which was puzzling in the extreme.