a) These telescopes must make observations above much of the water vapor in the atmosphere because water can block infrared rays.
Explanation:
Ground- based infrared telescopes are placed in a high altitudes dry climates because the telescopes must make observations above much of water vapor since they cut and block them off.
Telescopes are devices that are used to observe very distant objects.
An infrared telescope is sensitive to infrared rays.
Infrared rays are part of the electromagnetic radiations.
These rays are usually blocked off by the presence of water vapor.
Desert areas that lacks water vapor in the atmosphere are the most desired for sighting such facilities.
