In the following one word substitution question, select the alternative that best replaces the phrase "eating mud", that is, feeding on or consuming mud as a normal habit.

Introduction / Context:
This question tests your knowledge of specialised biological or zoological vocabulary expressed through one word substitutions. Different animals are often described by terms that reflect what they habitually eat, such as flesh, plants, fruits, or in this case, mud. Being able to decode such scientific sounding words is very useful for both general knowledge and science oriented competitive exams.

Given Data / Assumptions:

• The descriptive phrase is "eating mud".
• Four options ending in "-vorous" are given, each indicating a particular type of diet.
• The correct word must refer specifically to eating mud.
• The other options refer to eating other substances such as horses, fruits, or calcium rich materials.

Concept / Approach:
The suffix "-vorous" comes from the Latin "vorare", meaning to devour or eat. The prefix indicates what is eaten. "Limi" or "limus" relates to mud, so "limivorous" means feeding on mud. "Equi" relates to horses, "calci" to calcium or lime, and "fructi" to fruit. Therefore, only "limivorous" matches the meaning "eating mud". Many worms and some aquatic animals are described as limivorous because they ingest mud while feeding on organic matter within it.

Step-by-Step Solution:
Step 1: Notice that all options end with "-vorous", indicating a pattern of eating or feeding. Step 2: Focus on each prefix to see what type of food it indicates. Step 3: Recall or infer that "limi" is linked with mud or slime, giving "limivorous" as mud eating. Step 4: Match this with the question phrase "eating mud". Step 5: Exclude all other options because their prefixes point to different foods.

Verification / Alternative check:
Consider related words: "fructivorous" clearly contains "fructi", which is similar to "fruit", making it fruit eating. "Calcivorous" suggests eating substances rich in calcium or lime. "Equivorous" would imply feeding on horses, which is unusual and not the idea given in the question. By elimination and root analysis, "limivorous" remains the only logical match for mud eating. This linguistic cross check supports the choice of Option B.

Why Other Options Are Wrong:

• Option A, "Equivorous", would be associated with eating horses (equus means horse) and has no relation to mud.
• Option C, "Calcivorous", means feeding on calcium rich material or limestone, not mud in general.
• Option D, "Fructivorous", refers to fruit eating animals and is obviously unrelated to mud.

Common Pitfalls:
When faced with unfamiliar scientific terms, students sometimes guess based only on how impressive a word sounds, rather than analysing its parts. Another common error is to confuse similar sounding prefixes, especially when under time pressure. To avoid these mistakes, practise breaking down long words into roots and suffixes and connect them with simpler English words or Latin roots you already know. This skill makes you much more effective in tackling one word substitution and vocabulary questions.

Final Answer:
The correct one word substitution for "eating mud" is Limivorous, so Option B is the right answer.