People can often see a talking parrot on a TV show, in a movie, or even in someone's home. The parrot has learned ____ (copy) sounds that people make. Dolphins, bats, and some other animals also copy sounds. Now we can add elephants ____this list of copycats (盲目模仿者).

    Dr. Joyce Poole is an expert,____studies the sounds of elephants. While she was in Kenya, she would hear strange noises ____ (make) by Mlaika after sunset. Mlaika was____ 8-year-old African elephant and it lived near a highway.

    Dr. Poole says that she couldn't tell the ____ (different) between Mlaika's call and the ____ (distance) truck noise. Why did it copy the sounds of the trucks driving by? Animals that are able to copy sounds may enjoy ____(practice) new sounds. When they ____ (keep) outside of their natural environment, they may copy unusual sounds. 

    So far Dr. Poole ____(spend) 18 years with two female Asian elephants. Asian elephants make sounds like birds to talk with one another.

    Parrots, dolphins, humans, and elephants show that being a copycat is one way that animals and people make new friends and keep old ones.

求值：$\frac{\tan 49°+\tan 11°}{1-\tan 49°\tan 11°}$=（　　）

将下面一个长句变成四个短句，可增删词语，但不得改变原意。

由推进舱、返回舱、轨道舱和附加段组成的中国第五艘搭载太空人的神舟十号飞船在由长征二号F改进型运载火箭神箭发射升空后，在轨飞行了15天。