With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: Between 1853 and 1862, there were a number of uprisings against the Brooke government but all were successfully contained with the aid of local tribes. To guard against future uprisings, a series of forts were constructed to protect Kuching, including Fort Margherita, completed in 1871. Brooke had then taken control of Sarawak, which made the the defences largely superfluous.
text_B: As the 1870's began, does it sound like Brooke's alliances with the local tribes appeared to be stable and reliable?
YES.