Millet began to differentiate from rice about 50 million years ago, and the genomic structure after differentiation still showed significant colinearity. Researchers found that millet chromosomes 2 and 9 were composed of rice 7 and 9, respectively, and 3 and Chromosome 10 was fused. At the same time, they found that the two fusion events also occurred in the sorghum chromosome, so the researchers speculated that the two chromosomal fusion events should occur before sorghum differentiated from millet. Which of the following premise is needed for the above reasoning? ['Sorghum differentiation from millet occurs after millet differentiation from rice.', 'The collinearity between sorghum and millet is less than the collinearity between sorghum and rice.', 'It is unlikely that chromosomes 3 and 10 will be separated after fusion.', 'Another chromosomal fusion event occurred after millet was differentiated from rice.']