I would bugger off #2.
A change from a negative rate to a lesser negative rate is NOT "positive rate".
A combination of #1 & #3. I'd want to see the VSI actually showing positive and the Alt start to show an increase.
Don't rely on just one indication. If you do, you are not looking at the whole picture.
For example, I've done plenty of takeoffs from runways where after liftoff the Alt is showing an increase but the VSI is showing a decrease yet i'm climbing away.
Why? Downslope on the runway... Takes a second or two for the VSI to get back up to "positive". Strange but true.