Bring out the only correct statement in context with Uranium:

Both U-235 and U-238 are fissile but only U-235 can sustain chain reactions

Only U-235 is fissile and can sustain chain reaction but U-238 is fertile

U-238 can be used in chain reactions only after extracting U-235 from it

Uranium enrichment is a process where concentration of U-238 is increased using some chemical processes