help!

[rojeen]

there is an error (one and only) in this sentence :

A researcher, which study has sparked controversy, has been asked by his peers not to publish it, which is unacceptable.

I don't understand where the error is. Can you help me?

thank you :)

[Josef Essberger]

A researcher, WHOSE study has sparked controversy, has been asked by his peers not to publish it, which is unacceptable.

maybe