In the following question, out of the four alternatives, select the one word which is the best substitute for the phrase 'Phobia of dogs'.

Introduction / Context:
This one word substitution question checks your familiarity with medical style terms for specific phobias. A phobia is an intense, irrational fear of a particular object, situation or creature. In this case, you must select the technical term for an abnormal, strong fear of dogs. Such terms often appear in vocabulary lists for competitive exams and in general knowledge of psychology related words.

Given Data / Assumptions:
- Phrase to replace: 'Phobia of dogs'.
- Options: 'Orophobia', 'Cynophobia', 'Vatrachophobia', 'Phemophobia'.
- Only one option should specifically refer to fear of dogs.

Concept / Approach:
The term 'Cynophobia' comes from Greek roots: 'kyon' or 'cyno' meaning dog, and 'phobia' meaning fear. Therefore, 'cynophobia' literally means fear of dogs. 'Orophobia' would relate to mountains or mouths depending on the root, but it is not the standard term for fear of dogs. 'Vatrachophobia' refers to a fear of frogs or amphibians (from 'batrachia'). 'Phemophobia' is not recognised as the standard name for dog phobia either. So we should choose the option containing the 'cyno' root associated with dogs.

Step-by-Step Solution:
Step 1: Recall that 'phobia' in medical or psychological terms means intense irrational fear. Step 2: Identify the root in 'Cynophobia': 'cyno' or 'kyon' is linked to dogs in words like 'cynology' (study of dogs). Step 3: Match 'Cynophobia' with 'phobia of dogs' as fear of dogs. Step 4: Note that 'Orophobia' does not have the 'cyn' root and is used differently in medical terminology. Step 5: Note that 'Vatrachophobia' is associated with frogs and amphibians, and 'Phemophobia' is not a standard dog related term.

Verification / Alternative check:
Think of how related fields use these roots: 'cynic' originally referred to a member of a Greek philosophical school associated symbolically with dogs, and 'cynology' is the scientific study of dogs. This root connection strengthens the association between 'cynophobia' and dogs. In contrast, the other options lack any common root that suggests dogs, so they cannot accurately represent fear of dogs.

Why Other Options Are Wrong:
'Orophobia' is wrong because it is typically associated with fear of heights, mountains or swallowing, depending on context, not with dogs. 'Vatrachophobia' (more commonly 'batrachophobia') refers to fear of amphibians such as frogs, not dogs. 'Phemophobia' is not the standard term used for fear of dogs and does not contain any root that suggests dogs, so it is not the correct one word substitution.

Common Pitfalls:
Many students guess phobia words purely based on sound, but a better strategy is to learn common roots: 'arachno' for spiders, 'hydro' for water, 'acro' for heights, 'cyno' for dogs and so on. Recognising these roots allows you to decode new terms even if you have not memorised every phobia name. In exams, whenever you see 'cynophobia', link 'cyno' with dogs to recall its meaning quickly.

Final Answer:
The correct one word substitute for 'phobia of dogs' is Cynophobia.