When does a temp. buff to CL affect a spell?

[Meager Rolmug]

A PC has a way to temporarily increase his caster level checks. So does...

A. It affect only the spells cast during the buff's use, but the spells keep their boost to overcome SR during their entire duration.

B. It only affect spells when an enemy encounters the spell while the buff is being used.

C. It only applies to spells that are both cast AND an enemy encounters it while the buff is in use.

[Gisher]

Caster level matters when the spell is cast. Once cast, the spell's parameters are set and won't change if the CL buff runs out.