Which observational tool astronomers arno penzias and robert wilson discover the existence of the cosmic microwave background (cmb)?

Holmdale Horn Antenna

Explanation:

In 1984, while working in the Bell Lab, the Holmdale Horn Antenna detected some signals thereby producing odd sounds which was felt to be coming from all parts of the sky. Both Wilson and Penzias, when heard the noise for the first time thought that it was due to the pigeon living in the antenna. They removed the pigeon avoid disturbance. Later they found CMB that predicted the echo of birth of Universe.

Hence, Holmdale Horn Antenna helped astronomers Arno Penzias and Robert Wilson discover the existence of the cosmic microwave background

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms