Answer
There are 4 elements which would emit radiatio in the visible part of the spectrum: Ba, Ca, K and Na.
Work Step by Step
The wavelength range of the visible part of the electromagnetic spectrum is from $400nm$ to $750nm$.
Now we compare the characteristic wavelengths of the elements with the wavelength range of the visible part to see which wavelength fits in the range.
There are 4 elements whose characteristic wavelengths fit in the range of the visible part: Ba $(455.4nm)$, Ca $(422.7nm)$, K $(404.7nm)$ and Na $(589.6nm)$
These are the elements which would emit radiation in the visible part of the spectrum.
