You are the network technician at domain.com. Your newly appointed TestKing trainee wants to know when glare occurs.
What will your reply be?

A.
When echo cancellers fail to synchronize.

B.
When two phones go off-hook at the same time.

C.
When two optical wavelengths collide in the same fiber.

D.
When both ends of a telephone line or trunk experience echo.

E.
When both ends of a telephone line or trunk are seized by different users.