There are two kinds of division of labor: that based on age and that based on sex. Division of labor by age results in the obvious biological fact that human beings【C1】______ three major periods of development. In childhood, the human is in large part dependent upon adults for food, shelter, and other【C2】______ he has neither the strength nor the skills to【C3】______ for himself. Children, in most societies, have only light tasks as helpers【C4】______ adults or none at all, and when duties are【C5】______ , these are often regarded as educational, to prepare the child for his adult【C6】______ . Adulthood is ordinarily the period of greatest vigor and ability. The adult man or woman【C7】______ on full responsibility for the duties of his/her sex and special occupation. In many societies, in particular those【C8】______ the technology requires physical strength and stamina, the adult in the prime of life【C9】______ a dominant role and is often assigned the more responsible position in the group. Old age, since it inevitably brings【C10】______ a loss in muscular vigor and a decline in sight, hearing and coordination, again results in a change in occupational status. This does not necessarily mean that the old lose【C11】______ many societies make full use of their older members' experience and wisdom and employ them to direct the efforts of the more vigorous【C12】______ no-so-experienced adults. Sex division of labor is more difficult to【C13】______ for in strictly biological terms. A careful survey of the division of labor by sex lends little support to the often-repeated 【C14】______ that women are 【C15】______ only for occupations that require relatively little skill or intelligence. In recent years women, freed from economic【C16】______ to men, have shown themselves fully【C17】______ in nearly all professions in which they have been given the opportunity to participate. Man's wider range of occupation and the fact【C18】______ he very often occupies the more important positions of leadership in human societies, is probably【C19】______ due to his allegedly superior intelligence than to his greater freedom from the biological function of childbirth and the necessarily【C20】______ duties in the care of infant. 【C1】