A、Koala has no fingerprints. B、They are similar to human fingerprints. C、They cannot be observed by microscope. D、They are in di

The koala is broadly similar in appearance to the wombat(袋熊), but has a thicker coat, much larger ears, and longer limbs. The koala has large, sharp claws to assist with climbing tree trunks.(19)Its weight varies from about 14kg for a large southern male, to about 5kg for a small northern female. Its five fingers are arranged with opposable thumbs, providing better gripping ability. The first two fingers are positioned in apposition(并列)on the front paws, and the first three fingers for the hind paws. The koala is one of the few mammals that have fingerprints.(20)Koala fingerprints are similar to human fingerprints: even with an electron microscope, it can be quite difficult to(distinguish between the two. Koala can walk along a branch. Koalas also walk on all four legs when walking on the ground. The brain in the ancestors of the modern koala once filled the whole cranial cavity, but has become drastically reduced in the present species, a degeneration scientist suspects it is an adaptation to a diet low in energy. It’s generally a silent animal, but males have a very loud call that can be heard from almost a kilometer away during the breeding season.(21)When under stress, koalas may make a loud cry, which has been reported as similar to that of a human baby. There is little reliable information about the lifespan of the koala, but in captivity they have been observed to reach the age of 18 years.
19. Which of the following cannot be the koala’s weight?
20. What can we know about koala’s fingerprints?
21. What can we learn about Koala’s voice?