The difference between narrow-beam and broad-beam conditions is that:

Narrow-beam conditions imply that only the unscattered radiation reaches the detector, while broad-beam conditions imply that both scattered and unscattered radiation reach the detector.

Narrow-beam conditions imply that both scattered and unscattered radiation reach the detector, while broad-beam conditions imply that only the unscattered radiation reaches the detector.

Narrow- and broad-beam conditions relate only to source size.

Both terms depend on the film and screen combination.

None of the above.