Four different uracil auxotrophs of Neurospora, a eukaryotic mold, are tested for growth on uracil and uracil precursors. The data are shown in the following table. A plus sign (+) means growth. Compound Mutant 1 Mutant 2 Mutant 3 Mutant 4 A +−+− B +−−− C +++− D −−−− Uracil ++++ -Neurospora can be grown as haploids or diploids. Haploid mutants 1 and 2 are fused to make a diploid. If both 1 and 2 carry recessive mutations, on which compounds will the diploid be able to grow?