Correct Answer:
A. to
The correct preposition to use with 'fatal' when referring to the outcome or consequence for something is 'to'. Therefore, 'fatal to our plans' correctly conveys that the absence caused the plans to fail or be destroyed.
- A. 'to' is correct because 'fatal to' is the standard idiomatic expression indicating a destructive effect on something.
- B. 'for' is incorrect; while 'for' can indicate purpose, it doesn't fit the destructive meaning of 'fatal' in this context.
- C. 'from' is incorrect as it implies origin or separation, which doesn't apply here.
- D. 'after' is incorrect as it denotes sequence in time, not consequence.