Question

. . . by 1590 the principal actors stay in the city. The burgeoning population of London provides them with large audiences, especially when they be­come established at their respective theaters: the Lord Admiral's Men at the Rose and the Lord Chamberlain's Men at the Globe. Only when the theaters are closed by the authorities because of the plague—in 1581–82, 1592–93, and 1603–4—do the London companies start to tour again, from Bath to Not­tingham. Ironically, one place they do not play is Stratford-upon-Avon.

–The Time Traveler's Guide to Elizabethan England,
Ian Mortimer

Which factor directly influenced the actors' decision to resume their travels?

the population of London
the popularity of plays in Bath and Nottingham
the outbreak of the plague
the theater ban in Stratford-upon-Avon

Answer 1

the outbreak of the plague

The passage says the companies only began touring again when the theaters were closed because of the plague, so the plague closures directly prompted their travel.