Which scan would be ideal to exam the spleen and liver. a ct scan, spleen and liver scan(nuclear), or sonogram?

Depends for what: Ct is probably the best out of the ones you listed because it gives high spacial resolution and contrast. Mri would give even better contrast but this is likely not necessary. Us will show the size of each organ and any large lesions; it does not have associated radiation like ct or nuclear med scan. Nuc med scans typically used for specific purpose only, not general evaluation.