What correction would you make to fix the punctuation error in the following sentence?

leeann studied all weekend; therefore: she did well on her algebra test.
a) replace the colon after “therefore” with a comma.
b) replace the semicolon after “weekend” with a comma.
c) replace the semicolon after “weekend” with a colon.
d) replace the colon after “therefore” with a semicolon.