In the following question, out of the four alternatives, select the word which is similar in meaning to the phrasal verb "to astound", meaning to greatly surprise or amaze someone.

Introduction / Context:
This vocabulary question asks for a word or phrase similar in meaning to "to astound". The verb "astound" means to shock or greatly surprise someone, often leaving them amazed or at a loss for words. The correct option will express a strong effect on the mind, not calmness or peace. Recognising the emotional intensity of "astound" is key to choosing the right synonym.

Given Data / Assumptions:

• Target phrase: "To astound".
• Options: To Bewilder, To Tranquil, To Placid, To Serene.
• We assume standard meanings: astound = amaze or greatly surprise.
• The correct choice should indicate a strong mental impact, such as confusion, amazement, or shock.

Concept / Approach:
"To astound" and "to bewilder" both describe strong mental reactions. "To astound" means to fill someone with sudden wonder or surprise; "to bewilder" means to confuse or puzzle completely, often as a reaction to something unexpected. While not perfectly identical, "to bewilder" is much closer in intensity and effect than verbs associated with calmness. The other options are derived from adjectives "tranquil", "placid", and "serene", all of which are connected to peace and calm, the opposite of being astounded.

Step-by-Step Solution:
Step 1: Define "to astound": to greatly surprise or amaze, sometimes to the point of leaving someone briefly confused or speechless. Step 2: Examine "To Bewilder." This means to confuse someone deeply, often because something is surprising or hard to understand. It suggests a strong mental impact. Step 3: Observe that both "to astound" and "to bewilder" involve a powerful reaction to something unexpected or extraordinary. Step 4: Examine "To Tranquil." This is incorrect because "tranquil" is an adjective meaning calm or peaceful; "to tranquil" is not standard usage as a verb. Step 5: Examine "To Placid." "Placid" is an adjective meaning calm or undisturbed; again, "to placid" is not a standard verb and suggests calmness, not amazement. Step 6: Examine "To Serene." "Serene" is another adjective meaning calm and peaceful; "to serene" is not a normal verb form and is conceptually opposite to surprise or shock. Step 7: Conclude that "To Bewilder" is the best available equivalent to "To Astound" among the given options.

Verification / Alternative check:
Consider example sentences: "The news of their sudden victory astounded everyone," and "The news of their sudden victory bewildered everyone." In both cases, people are left mentally shaken or confused by unexpected information. By contrast, "The news tranquil everyone" or "The news placid everyone" do not exist in English and, even if forced, would suggest calmness, which opposes the meaning of "astound". This shows that "To Bewilder" is the only sensible choice.

Why Other Options Are Wrong:
"To Tranquil", "To Placid", and "To Serene" are all based on adjectives that describe peaceful, calm states. None of these words, even in their correct forms "tranquil", "placid", or "serene", convey the idea of shock, amazement, or confusion. They move in the opposite emotional direction from "astound".

Common Pitfalls:
Some students may hesitate to choose "To Bewilder" because they think bewilder only means confused, not amazed. However, in many contexts, people are bewildered because something is so astonishing or unexpected that their mind cannot immediately process it—very similar to being astounded. Another pitfall is assuming that all answer options are correctly formed verbs; here, only "To Bewilder" corresponds to a normal verb, and that itself is a clue.

Final Answer:
The word similar in meaning to "To Astound" is To Bewilder.