In the following question, the sentence is given with a blank to be filled in with an appropriate word. Select the correct alternative out of the four and indicate it by selecting the appropriate option: More than thirty years have now passed ______ I had my first flight.

Introduction / Context:
This preposition question checks whether you can correctly express the idea of time elapsed from a specific event in the past up to the present. English frequently uses the word “since” with present perfect tense to mark the starting point of such a time period.

Given Data / Assumptions:

• The sentence reads: “More than thirty years have now passed ______ I had my first flight.”
• The verb phrase “have now passed” is in the present perfect tense.
• We must fill the blank with a time connector.
• Options: since, after, while, when.

Concept / Approach:
The present perfect (“have passed”) is often used with “since + past time clause” to indicate time duration from a point in the past until now. The structure “have passed since I had my first flight” is standard English. Using “after”, “while”, or “when” in this position would either require a different verb form or change the meaning of the sentence.

Step-by-Step Solution:
Identify the pattern: “More than thirty years have now passed … I had my first flight.”We want to say “from the time I had my first flight until now”.The correct connector for this meaning with present perfect is “since”.Check “after”: “have passed after I had my first flight” is unidiomatic; we would say “thirty years after I had my first flight, I did X”, not “have passed after”.Check “while”: used for something happening at the same time; “while I had my first flight” does not fit.Check “when”: “have passed when I had my first flight” is grammatically incorrect in this structure.So, “since” is the correct choice.

Verification / Alternative check:
Insert the chosen word: “More than thirty years have now passed since I had my first flight.” This is exactly how native speakers describe the time elapsed between a past event and now. For example: “Ten years have passed since I last visited my school.” The pattern “have passed since + past clause” is standard and well-formed.

Why Other Options Are Wrong:
“After” typically leads to a clause or phrase describing what happens next, not the entire time period until now. “While” describes two actions happening at the same time, which is not the idea here. “When” introduces a point in time but does not fit grammatically with “have passed” in this position; we would need a different structure like “I remember when I had my first flight.” Thus, only “since” correctly expresses “from that time until now”.

Common Pitfalls:
Students sometimes confuse “since” and “after” because both refer to time following an event. However, “since” works with present perfect to measure duration up to the present, whereas “after” is used to sequence events in the past or future. Recognising this pattern will help you in many tense and preposition questions.

Final Answer:
The correct word to fill the blank is since.