The password of both users rosie and bobby has been set to the same password. Why their entries in $/$etc$/$shadow are different?

ubuntu@ubuntu: $ sudo passwd rosie

New password:

Retype new password:

passwd: password updated successfully

ubuntu@ubuntu: $ sudo passwd bobby

New password:

Retype new password:

passwd: password updated successfully

ubuntu@ubuntu: $ sudo tail $-2/$etc$/$shadow

bobby: $6$$ gNxVzfKCeK$/$eaoWN$BRa$4$kc$9507$QcVsb$10$HFG$8$W$33$qOPu.ntPbXcsiZP$3$q$1$SEKNYzkGgUzuW$90$u

rosie:$$6$$$7$TA$4$w$1$hwN$8$p$1$b$6$jj$$29$qsEtZXWY$2$Ispp$3$mFlwQ$3$TjpLfGICW$1$Ka$/9$uULP$60$Tew$5$AqLKYdGOybme

a$.$ Because they belong to different groups and this is used to compose the password hash

b$.$ Because hashing functions produce different output even if the input remains the same

c$.$ Because the username is different and it is used to compose the password hash

$$ d$.$ Because the password is salted specifically for each user before composing the password hash