she/a yellow dress?

Решение:

1. she is wearing a yellow dress? — Это общий вопрос в Present Continuous.
2. No, she isn't wearing a yellow dress. — Отрицательный ответ на общий вопрос.
3. She's wearing a red dress. — Утвердительное предложение, уточняющее, что на самом деле надето.

Ответ: Is she wearing a yellow dress? No, she isn't wearing a yellow dress. She's wearing a red dress.