In the following question, choose the option that is similar in meaning to the given word: Pernicious.

Introduction / Context:
This vocabulary question asks for a synonym, that is, a word with a meaning similar to the given word pernicious. Such questions are very common in competitive exams because they directly test a learner's depth of vocabulary and sensitivity to shades of meaning. The word pernicious is often used in serious writing, for example in discussions about harmful habits, policies or influences, so understanding it is useful for both exams and general English.

Given Data / Assumptions:
- Target word: Pernicious.
- Options: Beneficial, Dangerous, Innocuous, Advantageous.
- We need the option whose meaning is closest to that of pernicious.
- The context is general vocabulary, not limited to any special technical field.

Concept / Approach:
Pernicious describes something that is extremely harmful, often in a gradual or subtle way. It can refer to habits, ideas, diseases or influences that cause serious damage. When comparing with the options, we look for a word that carries a clearly harmful sense. Dangerous means likely to cause harm or injury, which is close in meaning. Beneficial and advantageous both describe positive, helpful effects, while innocuous means harmless. Therefore, Dangerous is the correct synonym for pernicious in this set of options.

Step-by-Step Solution:
Step 1: Recall or infer the meaning of pernicious. It means highly harmful or destructive.Step 2: Examine the option Beneficial. It means producing good results or helpful effects, which is the opposite of harmful.Step 3: Check Dangerous. It means likely to cause harm, damage or injury, which aligns well with the harmful sense of pernicious.Step 4: Look at Innocuous. It means harmless or not likely to offend, again the opposite of pernicious.Step 5: Consider Advantageous. It describes something that gives benefit or advantage and is therefore positive, not harmful.Step 6: Among the four, Dangerous is clearly the closest in meaning to pernicious.

Verification / Alternative check:
We can test the word in example sentences. A pernicious habit slowly ruined his health sounds very similar to A dangerous habit slowly ruined his health. On the other hand, replacing pernicious with beneficial or advantageous produces nonsense because those words imply good effects. Using innocuous also changes the meaning completely because innocuous implies no harm. Hence, Dangerous is confirmed as the best synonym in ordinary usage when no fine technical distinction is required.

Why Other Options Are Wrong:
- Beneficial suggests something good for a person or situation, which directly contradicts the harmful sense of pernicious.
- Innocuous means harmless, mild or not offensive, which again is the opposite of pernicious.
- Advantageous refers to something that offers an advantage or gain and has a positive connotation rather than a negative one.

Common Pitfalls:
Students sometimes confuse pernicious with words that simply mean bad or unpleasant, without noting the strong idea of harm or damage. They may also be misled by unfamiliar spellings or pick an option that looks difficult on the assumption that it must be the right answer. A better strategy is to learn high frequency academic words like pernicious with their typical collocations, for example pernicious influence, pernicious effects or pernicious weed, so that the negative and harmful sense becomes clear and memorable.

Final Answer:
The word that is similar in meaning to pernicious is Dangerous.