Answer:
B. Sebastian and Antonio making plans to murder Alonso.
Explanation:
There were many telltale signs that painted Shakespeare's "The Tempest" as a tragedy from Acts 1 and 2 (besides, duh, it's Shakespeare, we all know it's ending with someone and/or everyone dying).
Perhaps because the play essentially opened highlighting the severity of Prospero's treatment to his loyal servent, Caliban. This showed the flaws of Prospero's nature.
Then you had Miranda's ignorance towards her looming fate, and her father's recklessness.
Then you have the fact that the play practically opens with murder, with the ongoing plot.
The storm wasn't so much the ill-boding of a tragedy as it was one brother barking at another brother. The storm was raised just interrupt Antonio, the current duke, because Prospero, his bro, was technically the rightful duke.
Because the answers are a BIT limiting, I'd say B is your best option here. If there were a second choice, I wouldn't entirely eliminate D, but I can confidently state that D is less likely to be correct just because having multiple plots doesn't necessarily foreshadow the play's tragic roots, it just adds to the story leading UP to that. Again, having multiple plots doesn't neccesarily reveal tragedy, and if anything, it might even obscure the tragedy in the story for some time.
B is your best bet :)
D is a last resort.
The other choices are rather ludicrous.