Are the following sentences natural to a native ear?
[color=darkblue]1. The weak performance is attributable to a much higher than expected profit margin.
Can you hold on that for half an hour?
Every time I go in there, he must think that I came to ask a favor.
(1) is fine. I would change (2) and (3) to read:
Can you hold on to that for half an hour? I assume you are asking someone not to let it (that) go
Every time I go in there, he must think that I have come to ask a favor.
Why did you choose the present perfect over the past tense?