Acomparison and contrast article is best for which of the following? when a single subject is extremely complicated when an argument is especially heated when there are narrative elements to explain when there are two related subjects to discuss or review

1. in which sentence is the underlined portion a predicate nominative? for astronauts, going into space to repair orbiting equipment becomes a challenge. for astronauts, going into space to repair orbiting equipment becomes tricky. for astronauts, going into space to repair orbiting equipment becomes challenging. for astronauts, going into space to repair orbiting equipment becomes frequent.