circadian rhythm

[AVIATROZ]

Q.How long is a free running circadian rhythm?
a. 24 hr
b. 48hr
c. 25hr
d. 29hr

ANS- b

but i read in oxford book as" CIRCARDIAN RHYTHM WILL FREE RUN TO A PERIODICITY OF ABT 25 HRs."

plz explain if i m getting the concept wrong somewhere.
thanks

[iwrbf]

I don't know about your books but in my knowledge, the circadian rhythm is 25 hours. This is scientific consensus as far as I know as it is the time period a human adapts to without external reference to the time of day.

Kind regards,
Peter

[AVIATROZ]

thanks for the reply............even acc. to me it 25 hrs.....but don`t knw why is it giving wrong in the question....................i hope there is no other concept behind it