Looks like you didn’t build/install with any UI components.
From the file you uploaded:
yahya@yahya-VirtualBox:~/Geant4/Examples/B1-build$ ./exampleB1
Available UI session types: [ GAG, tcsh, csh ]
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Visualization Manager initialising...
Registering graphics systems...
You have successfully registered the following graphics systems.
Current available graphics systems are:
ASCIITree (ATree)
DAWNFILE (DAWNFILE)
G4HepRep (HepRepXML)
G4HepRepFile (HepRepFile)
RayTracer (RayTracer)
VRML1FILE (VRML1FILE)
VRML2FILE (VRML2FILE)
gMocrenFile (gMocrenFile)
Followed by multiple instances of:
ERROR: Current scene handler not defined. Please select or create one.
I configured to use Qt and see:
Available UI session types: [ Qt, GAG, tcsh, csh ]
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You have successfully registered the following graphics systems.
Current available graphics systems are:
ASCIITree (ATree)
DAWNFILE (DAWNFILE)
G4HepRep (HepRepXML)
G4HepRepFile (HepRepFile)
RayTracer (RayTracer)
VRML1FILE (VRML1FILE)
VRML2FILE (VRML2FILE)
gMocrenFile (gMocrenFile)
OpenGLImmediateQt (OGLIQt, OGLI)
OpenGLStoredQt (OGLSQt, OGL, OGLS)
OpenGLImmediateX (OGLIX, OGLIQt_FALLBACK)
OpenGLStoredX (OGLSX, OGLSQt_FALLBACK)
RayTracerX (RayTracerX)