She had only just put the telephone down when the boss rang. A. Only when she put the telephone down and the boss rang. B. Hardly had she put the telephone down when the boss rang. C. It was

Only when she put the telephone down and the boss rang.

Hardly had she put the telephone down when the boss rang.

It was not until the boss rang back did she put the telephone down.

Not until she had put the telephone down that she let it ring when the boss rang.