|Question 17Verbal

Source Texts

Text
A region of the Soviet Union encompassing the present-day city of Sukhumi, Georgia, the Abkhazian-speaking Abkhaz Autonomous Soviet Socialist Republic was in fact only nominally autonomous. President Mikhail Gorbachev's reforms, by helping the Abkhaz Republic and other Soviet republics established along ethnolinguistic lines assert their prerogatives,        to the Soviet Union's breakup.
Which choice completes the text so that it conforms to the conventions of Standard English?
contributing
A
having contributed
B
contributed
C
which contributed
D