at or on, or else

[ggomad]

Kindly review the following question I struck upon in my studybook.

All applicants need go through medical exams ____ the instruction of the HR department, or else they will not be considered for any position.

A) to B) on C) for D) at

I thought both B and D could be correct. My studybook says the answer is D without decent explanation. It's kind of confusing.
What would you advise me?

In which similar context can "on" be used, and what differences should I take notice to distinguish these two difficult prepositions in the above sentence or any other similar ones?

[Casiopea]

[quote="ggomad"]Kindly review the following question I struck upon in my studybook.

All applicants need (to) go through medical exams ____ the instruction of the HR department, or else they will not be considered for any position.

A) to B) on C) for D) at

I thought both B and D could be correct. My studybook says the answer is D without decent explanation. It's kind of confusing.
What would you advise me?

In that context, at means, with reference to; as per, in accordance with. On in that context refers to, based on.

In which similar context can "on" be used, and what differences should I take notice to distinguish these two difficult prepositions in the above sentence or any other similar ones?

Good question! It's often not that easy to tell. :( Mind you, as per (the) instruction is a common phrase. :)

All the best,

[ggomad]

Thanks for clearing things up!
You really help me sleep light-hearted.^^

[Casiopea]

Thanks for clearing things up!
You really help me sleep light-hearted.^^

Honestly? That's fabulous! :D You're welcome. :D

[yulia]

These prepositions is indeed a difficult thing. I mean that most of the times when you think that you were right, you prove to be wrong. I know that it's all a matter of time, but still...