FBI right to refuse to answer questions

[dvduval]

Suppose the FBI feels there is 50+% chance that someone on the House judiciary committee, like Trey Goudy, is indicated in one or more of the following:
1. Sharing information with subjects of the investigation (who may even have a sealed indictment against them).
2. Receiving guidance from indicted persons
3. Is himself subject of indictment, or a future witness
4. Is Compromised in some way

What is the legal basis for answering or refusing to to answer questions before the committee? It seems that even providing any indication that the subject (ex. Trey Gowdy) is under investigation would in itself be problematic, and of
Course this is why I thought an independent counsel is prudent, and more importantly the independent counsel can be consulted before someone like McCabe answers questions. So McCabe can stand up there and say that he will defer any questions to the independent counsel that pertain to anything remotely related to the Russia investigation.

[RDANGELO]

2. Well, McCabe was in front of the House intel committee for 7.5 hours today.

They were trying to figure out if it would be worth it to to bring him out in public to further their attempt to discredit the Mueller investigation. I imagine he replied a lot with he will not comment on an active investigation. It really makes no sense to do this when there is an ongoing inspector general's investigation where they will find out everything they need to know.

[marylandblue]

3. The FBI can refuse to answer questions about ongoing investigations

Grand jury investigations are secret. Only the prosecutor and the grand jury itself know the details until indictments are unsealed. It doesn't matter who they are investigating.