E7F11:What sets the minimum detectable signal level for a direct-sampling software defined receiver in the absence of atmospheric or thermal noise?

Direct answer summary (2024-2028 NCVEC pool)

The official correct answer for E7F11 is Reference voltage level and sample width in bits.

The key fact is Reference voltage level and sample width in bits. Match that fact to the exact condition in the question; the other choices describe a different rule, band, component, or operating situation.