Answer:
"tain", "duct", "viv", "Typo"
Step-by-step explanation:
The roots or base-words can be obtained by finding the suffix/prefix.
Retainer: "tain" because -Re is prefix and -Er is suffix
Inductive: "duct" because -In is prefix and -Ive is suffix
Convivial: "viv" because -Con is prefix and -Ial is suffix
Typography: "Typo" because -graphy is suffix.