Are you online? Are you at home?
Is she on her phone? Is she alone?: Using To Be in questions.
We need: the verb to be + the pronoun (I, you, he).
Necesitamos la forma de “ser o estar” (to be) y “el pronombre” (yo, tú, él – I, you, he). Recuerda, en inglés siempre vamos a poner el pronombre.
We always put the pronoun:
No: Is at home?
Yes: Is she at home?
So, for example: