HSA accounts are different from FSA in that

A HSA accounts allow contributions to be saved for the future and FSA accounts do not.

B HSA accounts allow contributions to be saved long term and HSA accounts do not

C FSA accounts allow for medical expenses to be paid using pre-tax dollars and HSA accounts do not.

D HSA unts allow for medical expenses to be paid using pre-tax dollars and FSA accounts do not.

This topic confuses me.