In which sentence is the underlined portion a predicate nominative?

a. for astronauts, going into space to repair orbiting equipment becomes "challenging"
b. for astronauts, going into space to repair orbiting equipment becomes "frequent"
c. for astronauts, going into space to repair orbiting equipment becomes "a challenge"
d. for astronauts, going into space to repair orbiting equipment becomes "tricky"

Answer asap explain your answer read the explicit message of the "rain barrels" video: you can use water from your rain barrel for a lot of different things around the home and garden. which is the best textual evidence to use to support this message? i use it to fill my fish tank, even to wash the car if you want to. so not only is the rain barrel water free, but it’s also free of chlorine and minerals. a rain barrel is a small investment for big dollar and environmental benefits. one of the benefits of a rain barrel is it holds that first bit of rain that’s coming off the roof or your driveway and prevents it from running into streams and causing erosion from high flows of water.