In the following passages the numbered gaps indicate missing words. Against each number in the below each passage, four options are offered in columns lette...

In the following passages the numbered gaps indicate missing words. Against each number in the below each passage, four options are offered in columns lettered A to D. choose the word that is the most suitable to fill the numbered gap in the passages.
Birds are instantly recognizable -81- perhaps because of their ability to -82-. Some people might consider their shape the most distinguishing -83-. Everyone, however, agrees on the characteristics that a bird possesses: two -84-, feathers two legs, a toothless -85-, warm blood, and the ability to -86- eggs. The modern system of -87- birds is like a pyramid, with the base formed by 8,514 different -88-. A convenient -89- of this system recognizes a group of birds which does not normally -90- with other groups.
One of the most precious gifts human kind has been given is the power to -91-. With it, we pass vital -92- to one another either -93- or by non-vocal methods, such as -94-. Freedom of -95- is in fact, a widely contested issue throughout the world some have therefore, assumed that communication is the -96- of only humans.
yet, research shows that animals -97- information in intricate ways that often baffle humans. Yes, they ''speak'', not with words, but through visual signals such as -98- tails, twitching ears, or -99- wings. Other forms of animal communication may involve the use of voice, such as a bark, a roar, a snari, or -100-. Some of the '' languages'' are obvious to humans, while others require much scientific study to detect.