is it correct: how long has it been on?

[Liza]

Hi,

Could you tell me which is the correct way to ask: when a lesson starter?:

How long has the lesson been on?
How long has the lesson lasted?
How long has the lesson taken?
or anythign else?

for example: for 5 minutes. But what is the correct question? I just can't find it out, in spite of the fact that it must be quite easy....

Thanks

[Mister Micawber]

.
'Lasted'. 'Taken' is OK, but indicates the speaker's dissatisfaction with the lesson or its length. 'Been on' is for TV shows, etc.
.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mister Micawber

[Jamie (K)]