This passage is a classic example of making a conditional reasoning error. In this specific instance, the passage makes a conditional statement, and then confuses the necessary and sufficient when making a conclusion. Let's see how:
Premise: Seeking job at international organization - > Spend lot of time travelling abroad
So far this is just a regular conditional statement, but now look at what they do with the conclusion.
Conclusion: Spend lot of time travelling abroad - > Seeking job at international organization
This is clearly an incorrect interpretation of necessary and sufficient. Spending lots of time travelling is a necessary prerequisite for seeking a job at an international organization. However, it is not sufficient to determine that someone is seeking a job at an international organization. It has this all mixed up.
Just because we have the following:
A - > B
Does not mean we can conclude
B - > A
The only things we know from A - > B are: A - > B and Not B - > Not A.
Answer choice D makes the exact same mistake as the passage:
Premise: Negotiating personal loan - > Go to bank
Conclusion: Go to bank - > Negotiating personal loan
I hope this helps. Please let me know if you have any other questions.