Regarding Type of Hydrogen bond lifetime autocorrelation function

GROMACS version: 2020
GROMACS modification: Yes/No

Dear Gromacs user ,
I am trying to calculate hydrogen bond lifetime autocorrelation using gmx hbond with -ac flag .

Now there are two ways of calculating hydrogen bond lifetime 1) intermittent and the 2) continuous one.

My question which one gromacs uses by default?

Thanks for your time and attention!