The phrase
"arduous challenge" means a difficult task or situation that requires a lot of effort and perseverance to overcome.
Full definition
While the two relate often and well about the type of work that goes on in the office, Mrs. Morin says the
most arduous challenge of their relationship comes in leaving work at work.
In Canada, the transition from print to digital news has been
an arduous challenge for labour relations.
As a result Amundsen's team actually gained weight during
the arduous challenge, and beat Scott to the pole by five weeks.
Couples face
an arduous challenge after the discovery or confession that one partner has cheated.
Finally, Amy also experiences
an arduous challenge with career, romance, and parenthood.