Complex sentence: They believe that the LDS Church has made unacceptable changes to doctrines and ordinances; thus, the members of the AUB see it as their responsibility to keep them alive in the form they were originally given and to live all the laws God has commanded.
Split into simpler sentences: They believe that the LDS Church has made unacceptable changes to doctrines and ordinances. The members of the AUB see it as their responsibility to keep them alive in the form they were originally given and to live all the laws God has commanded.