Problem 1396 (difficulty: 2/10)

Which sets are simply connected?

\(\displaystyle \R^2\setminus(\Z\times\Z) \qquad \R^3\setminus(\Z\times\Z\times\Z) \qquad \R^3\setminus\{(\cos t,\sin t,0): t\in\R\} \qquad \R^4\setminus\{(\cos t,\sin t,0,0): t\in\R\} \)

Give me another random problem!