What is the correct preposition for tricky problems? Why is the relative pronoun “which” and the relative clause being confused with each other? Can you tell me what is/are the “which?” Would you say

Load an object with difficulty

or

Lift an object by difficulty

(non-standard) Clearly the first? In my opinion, this is not a question about “what” but about what preposition to use with a particular noun. The point to learn from this is that you should always try to cut down the problem down to the bare essentials as this will make it easier to answer and easier to learn from the

answer.