Diagnostic radiological studies are indicated for low back pain:a.Routinely after 3 weeks of low back pain symptoms.b.To screen for spondylolithiasis in patients less than 20 years of age with 2 weeks of more of low back pain.c.When there is a suspicion of a space-occupying lesion, fracture, cauda equina, or infection.d.As a part of a pre-employment physical when heavy lifting is included in the job description