Originally astronomers classified those stars with the strongest hydrogen lines as 'A stars, stars with the next strongest lines as 'B' stars, the next strongest 'C' and so on. Eventually some letters were deemed unnecessary and dropped from the classification sequence. The letter assigned to a star is termed its spectral class. Assign a spectral class to each panel by following the procedure below: a) In the second column of Table 2, list the panel numbers from strongest HOD line at the top to weakest HO0 line at the bottom. b) Each panel corresponds to one of the following classes of stars: A, B,F,G, K and O. (We're skipping some letters here.) In the third column mark the letter that corresponds to each panel using the lettering scheme described above. Table 2 Panel Number Spectral Class strongest Ha line to weakest (Letter Designation) strongest A B F G K welkest