Concept:A semibreve equals 4 beats, and a quaver equals half a beat.Explanation:A semibreve is equivalent to 2 minims, 4 crotchets, or 8 quavers.Since each quaver is 21 beat, 8 quavers give 8×21=4 beats, which equals one semibreve.Answer:8 quavers make a semibreve.