Maleic acid plays the role of being a plant metabolite and has a systematic name of cis-2-butenedioic acid. What is its structural formula?

Structural formula of maleic acid, showing its two carboxylic acid groups.

Structural formula of maleic acid with one carboxylic acid group and one hydrogen atom.

Structural formula of a compound with two hydroxyl groups and a double bond.

Structural formula of a compound with carboxylic acid and hydroxyl groups.