massive galaxies suffer a stronger environmental effect than massive galaxies. The massive galaxies are likely old and dead before they are accreted on to dense environments, leading to them being less strongly affected by the environmental quenching and thus mainly dominated by the mass-quenching effect. In addition, at fixed radius, the median SSFR of all galaxies also drops significantly as the stellar mass increases more rapidly than for the star-forming galaxies. Learning from the median SSFRs of all and star-forming galaxies, the main environmental effect appears to move the less massive group or cluster galaxies out of the star-forming sequence to the quiescent population, leading to a suppression of the mean SSFR of all group or cluster galaxies.

### Quiescent Fraction $f_q$

Similar to Figure \[f6\], the quiescent fractions ($f_q$s) are plotted in Figure \[f7\]. The $f_q$s are also fit with a linear relation $f_q$ = $\alpha$ $\times$ ($r_p$/Mpc) + $\beta$ for $r_p$ $<$ 2.0 Mpc, and their best-fit parameter are listed in Table \[tab:fqfitting\]. There is one caveat to be noted: our comparisons are made at fixed physical cluster-/group-centric radius for different redshifts, but the physical sizes of clusters/groups change with time and also potentially with cluster/group richness. More 