The correct answer to the question "¿Qué hora es?" (What time is it?) would be one of the options that specifies a time. Among the options provided, "Son las tres" (It's three o'clock) is the appropriate response.
The other options do not indicate a time:
- "Es el domingo" (It's Sunday) refers to the day of the week.
- "Es quince" (It's fifteen) is unclear without context; it could refer to the 15th of a month, but it's not a time.
- "Son las una" (It's one o'clock) is correct, but it's less comprehensive unless the time is actually one.
So, "Son las tres" is the clear and correct choice for answering "¿Qué hora es?" if you're trying to indicate the time.