The amazing success of man as a(1)_____ is the result of the evolutionary development of our brains which has(2)_____, among other things, to tool-using, tool-making, the ability to solve problems by logical(3)______, thoughtful cooperation, and language. One of the most striking ways(4)_____ chimpanzees biologically resemble humans(5)_____ the structure of their brains. The chimpanzee, with his(6)_____ for primitive reasoning, exhibits a type of intelligence more like(7)_____ of humans than does any other(8)_____ living today. The brain of the modern chimpanzee is(9)_____ not too dissimilar to the brain that so many millions of years ago directed the(10)_____ of the first ape man. For a long time, the fact that(11)_____ man made tools was considered to be one of the major criteria to(12)_____ them from other creatures. It is true that the chimpanzee does not fashion his (13)_____ to a regular and set pattern—but then, primitive man,(14)_____ development of stone tools, undoubtedly poked around with sticks and straws, at which(15)_____ it seems unlikely that he made tools to a set pattern(16)_____. It is because of the close(17)_____ in most peoples minds of tools with man(18)_____ special attention has always been(19)_____ upon any animal able to use an object(20)_____ a tool; but it is important to realize that this ability, on its own, does not necessarily indicate any special intelligence in the creature concerned.
(1)

A. kind
B. series
C. species
D. tribe