Choose the most logical order of sentences from among the four given choices to construct a coherent paragraph.
A. The findings challenged the long-held assumption that intelligence is unique to humans.
B. The study observed that certain bird species demonstrate problem-solving skills on par with primates.
C. Researchers conducted experiments to test cognitive abilities in crows and parrots.
D. Their results showed remarkable similarities in logical reasoning and tool use between birds and great apes.