I'd say A is the top section. It also looks like it wants to sprout so if you leave it till the whitish part develops further you'll know soon.

These caudiciforms are often plants that sprout and flower before any rain falls in spring so you don't have to plant it yet, leave it to grow and show you

I agree with Nik about the orientation.

Thank you very much, you were both right. In 2 months it looks like this.