Select the related word from the given alternatives so that the analogy Bacteria : Microscope :: Moon : ? is correctly completed.

Introduction / Context:
This analogy checks understanding of the relationship between an object and the scientific instrument typically used to observe it clearly. Reasoning tests often include such questions to measure how well candidates connect real world knowledge, technology, and observation tools used in science.

Given Data / Assumptions:
First pair: Bacteria : Microscope. Second pair: Moon : ?. Words are used in their common scientific meanings. Exactly one option should play the same role for Moon as Microscope does for Bacteria.

Concept / Approach:
Bacteria are extremely small organisms that cannot be seen clearly with the naked eye. A microscope is the instrument specifically designed to magnify such tiny objects. Thus the relationship is object to instrument of observation. To complete the analogy, we must find the instrument typically used to observe the Moon in more detail than what the naked eye can provide. This leads naturally to an astronomical instrument.

Step-by-Step Solution:
Step 1: Understand Bacteria : Microscope. Bacteria are microscopic organisms that require a microscope to be observed clearly and studied. Step 2: Identify the type of relation. The relationship is between a very small object and the device used to observe it. Step 3: Extend the idea to Moon : ?. The Moon can be seen with the naked eye, but detailed observation of its surface, craters, and features requires a specific instrument. Step 4: Examine each option. Night: A time period, not an observing device. Earth: A planet that the Moon orbits, not an instrument. Satellite: A category that includes the Moon itself, not a device to look at it. Telescope: An optical instrument used to observe distant objects in the sky such as the Moon and planets. Sun: A star that illuminates the Moon but does not function as an observing tool. Step 5: Select the best match. Telescope clearly plays the same role for Moon that Microscope plays for Bacteria.

Verification / Alternative check:
We can rewrite both pairs as short sentences. A microscope is used to observe bacteria. A telescope is used to observe the Moon. This makes the parallel explicit and confirms that Telescope is the only option that maintains the same object to observing instrument relationship. Other options either represent celestial bodies or abstract concepts and therefore do not fit the analogy structure.

Why Other Options Are Wrong:
Night is a period of time during which the Moon is typically visible, but it is not an instrument for observation. Earth is the planet we live on and does not function as a device to observe the Moon. Satellite is a classification for orbiting bodies, and the Moon itself is a natural satellite. Sun is the star that provides light for the Moon but has no role as an observing tool.

Common Pitfalls:
Some candidates simply look for a word associated with the Moon, such as Night or Earth, without focusing on the precise nature of the relationship in the first pair. In analogy questions it is vital to define the relationship exactly and then search for the option that fits that same definition. Thinking in terms of object and instrument of observation helps avoid selection based on loose associations.

Final Answer:
The analogy Bacteria : Microscope :: Moon : ? is correctly completed by Telescope.