Marta es baja.
When we want to describe something or someone physically, we use the verb "ser" (to be). In this case the verb is in the present indicative.
Present indicative of the verb "ser" (to be):
- Yo soy
- Tú eres
- Usted es
- Él es
- Ella es
- Nosotros/as somos
- Vosotros/as sois
- Ustedes son
- Ellos/as son
MissSpanish