Which scenario is least likely to justify a continuance of trial?

a) plaintiff, a famous brain surgeon, who has sued his partner for breach of contract, has been invited to make a presentation at a brain surgery convention, and he wants to go.
b) plaintiff's attorney died two weeks ago, and new counsel just substituted in.
c) recent discovery showed that the owner of a building that collapsed had employed a previ-ously unknown structural engineer who should be sued.
d) plaintiff cannot depose defendant because defendant has become a defendant in a criminal case concerning the same factual basis as this civil action.