What Strategies and Electromagnetic Frequencies Are Thought to Be the MOST

Multiple Choice

What strategies and electromagnetic frequencies are thought to be the MOST logical for long-range communication across the universe with other intelligent beings?

A) explosion of nuclear devices at specific intervals and in specific patterns across Earth when closest to a nearby star
B) night-by-night photography of nearby stars at hydrogen Balmer wavelengths
C) continuous radio and microwave listening and transmitting at frequencies at which the natural radio sky noise background is low
D) X-ray surveys of space at appropriate times (e.g., when Earth is closest to nearby stars in its orbit) , in view of the penetrability of space at these wavelengths