The professor’s explanation was so ___that students lost interest quickly.
An _______speaker can explain difficult ideas very clearly and skillfully.
The abandoned airport project became a _______for the government.
Despite losing his job, he managed to ______by doing small freelance projects.
If \[ R=\{(x,y)\mid x,y\in \mathbb{R},\ x^2+y^2=1\} \] is a relation in \(\mathbb{R}\), then \(R\) is: