Hint: Band spectrum arises because of electron transition between the valence band and conduction band.Explanation:The band spectrum is caused by molecules. The energy levels of molecules are so close to each other that they combine to form a band. The valence band and conduction band are two types of bands. Electron transition between these two bands forms band spectrum.For example a spectrum of air. The bright bands are due to molecular oxygen (O\\\\(_2\\\\)), molecular nitrogen (N\\\\(_2\\\\)), and other molecules.So from the above example, it is clear that Option A is the answer.