The question asks you to fill in the blank in the sentence: "Everyone was ......... by surprise when she announced her plan to marry that boy." Understanding the context of this sentence is key to choosing the correct word. The primary phrase here is "by surprise," which typically pairs with the verb "taken" in English. The complete phrase "taken by surprise" is commonly used to describe a situation where someone is caught off guard or astonished unexpectedly.
Let's examine each option:
Based on this analysis, the phrase "taken by surprise" is the most appropriate choice in this context, aligning with standard English usage.
Conclusion: The correct answer is: taken.