Directions: Read the following text.Choose the best word(s) for each numbered blank and mark A, B, C or D on ANSWER SHEET 1.( 20 points ) In the past few decades, remarkable findings have been made in ethology, the study of animal social behavior. Earlier scientists had _1_ that nonhuman social life was almost totally instinctive or fixed by genetics. Much more careful observation has shown that _2_ variation occurs among the social ties of most species, showing that learning is a part of social life. That is, the _3 _are not solely fixed by the genes. _4_,the learning that occurs is often at an early age in a process that is called imprinting. Imprinting is clearly _5_ instinctive, but it is not quite like the learning of humans; it is something in between the two. An illustration best _6_ the nature of imprinting. Once, biologists thought that ducklings followed the mother duck because of instincts. Now we know that, shortly _7_ they hatch, ducklings fix _8_ any object about the size of a duck and will henceforth follow it. So ducklings may follow a basketball or a briefcase if these are _9_ for the mother duck at the time when imprinting occurs. Thus, social ties can be considerably _10_, even ones that have a considerable base _11_ by genetics. Even among the social insects something like imprinting _12_ influence social behavior. For example, biologists once thought bees communicated with others purely _13_ instinct. But, in examining a ¡°dance¡± that bees do to indicate the distance and direction of a pollen source, observers found that bees raised in isolation could not communicate effectively. At a higher level, the genetic base seems to be much more for an allª²purpose learning rather than the more specific responses of imprinting. Chimpanzees, for instance, generally _14_ very good mother but Jane Goodall reports that some chimps carry the infant upside down or _15_ fail to nurture the young. She believes that these females were the youngest or the _16_ child of a mother. In such circumstances, they did not have the opportunity to observe how their own mother _17_ for her young. Certainly adolescent chimps who are still with their mothers when other young are born take much interest in the rearing of their young brother or sister. They have an excellent opportunity to learn, and the social ties that are created between mother and young _18_ Goodall to describe the social unit as a family. The motherª²offspring tie is beyond _19_;there is some evidence to _20_ that ties also continue between siblings of the same sex, that is ¡°brotherª²brother¡± and ¡°sisterª²sister¡±. 1ª±A assumed B adopted C believed D surmised 2ª±A considerate B considerated C considerable D considering 3ª±A statues B statuses C statutes D statures 4ª±A What's more B Hence C But D However 5ª±A not B only C but D solely 6ª±A clarifies B classifies C defines D outlines 7ª±A than B before C when Dafter 8ª±A on B with C in D within 9ª±A appropriated B substituted C assigned D distributed 10ª±A varied B deviated C differed D altered 11ª±A fashioned B modified C influenced D affected 12ª±A may B should C must D can 13ª±A by B out of C from D through 14ª±A prove B make C turn D create 15ª±A otherwiseB still C yet D even 16ª±A one B sole C single D only 17ª±A looked B attended C cared D provided 18ª±A guide B cause C direct D lead 19ª±A limitation B imagination C doubt D expectation 20ª±A advise B hint C imply D suggest