To succeed in these tests it is absolutely necessary for you to aim at speed and accuracy.
(A) for you to aim at speed and accuracy.
(B) for you to aim for speed and accuracy.
(C) for you to go for speed and accuracy.
(D) that you aim speed and accuracy.
(E) that you should aim for speed and accuracy.
In my opinion, 'aim at' & 'aim for' both are correct.
'aim at' is used to pin-point at something in order to achieve something: you know the specific result and you know specific steps to achieve the result.
'aim for' is used in general; no specific outcome is expected and hence no specific directions.
For e.g., if you were a teacher you would DIRECT
your students to get very high marks and you know what exactly you mean by 'high marks
'. Hence you tell students, "aim at 80% marks to get this scholarship".
But if you were a guest in the class, you would preach students like "aim for good life". What is "good life" here? It varies from student to student.
Now, with this knowledge it should be clear that we should use "aim at" in our present scenario, because some one is clearly saying the importance of speed and accuracy.
Hope this is clear.
On a side note: there are still other usages of "aim" like "aiming to", etc,.
Because of these reasons, GMAT is slowly moving away from questions that are based on idioms; but to completely get rid of them, it takes considerable amount of time. Till then practice.