Hey guys :) does anyone know what is commonlit? If yes have you ever done the On the Education of Youth in America. If yes then pl tell me the answers pl :)

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.