Answer:
¿Está trabajando en el jardín?
Step-by-step explanation:
In this exercise, you have to complete the sentence using the present progressive tense. The Spanish present progressive tense is also called present continuous tense and it is used to talk about something that is happening now.
In the sentence given, you have to write "está" and not "estás" because "Ud." means "usted" and is the formal "tú". "Está trabajando" is the second person formal singular present progressive form of the infinitive verb "trabajar".