Care
Push.
There are two; they are dare and defy.The use of defy for challenge is illustrated by the use of civil disobedience to challenge unpopular laws.
A four letter word meaning the foundation of something is base.
call call cell cell hall hall hell hell gall gall gel gel hale hale gale gale cage cage lace lace lane lane cane cane lean lean clean clean glean glean gene gene glance glance lance lace eagle eagle lag lag hag hag gal can clan glen clang hang cee ( the letter C) lee gee nee lea leach leech ache allege all ell angel angle change heal hence glee henge eel heel
The four letter word for repairing something is mend.
dare
omen
Mend
hill
have
Hole Cave