单项选择题 The lack of printing regulations and the unenforceabiliy of British copyright lawin the American colonies made it possible for colonial printers occasionally to act aspublishers. Although they rarely undertook major publishing project because it wasdifficult to sell books as cheaply as they could be imported from Europe, printers in(5) Philadelphia did publish work that required only small amounts of capital, paper, andtype. Broadsides could be published with minimal financial risk. Consisting of only onesheet of paper and requiring small amounts of type, broadsides involved lower investmentsof capital than longer works. Furthermore, the broadside format lent itselt to subjects ofhigh, if temporary, interest, enabling them to meet with ready sale. If the broadside printer(10) miscalculated, however, and produced a sheet that did not sell, it was not likely to be amajor loss, and the printer would know this immediately, There would be no agonizingwait with large amounts of capital tied up, books gathering dust on the shelves, and creditorsimpatient for payment In addition to broadsides, books and pamphlets, consisting mainly of political tracts,(15) catechisms, primers, and chapbooks were relatively inexpensive to print and to buy.Chapbook were pamphlet-sized books, usually containing popular tales, ballads, poems,short plays, and jokes, small, both in formal and number of pages, they were generallybound simply, in boards (a form. of cardboard) or merely stitched in paper wrappers (asewn antecedent of modem-day paperbacks). Pamphlets and chapbooks did not require(20) fine paper or a great deal of type to produce they could thus be printed in large, costeffectiveeditions and sold cheaply. By far, the most appealing publishing investments were to be found in small books thathad proven to be steady sellers, providing a reasonably reliable source of income for thepublisher. They would not, by nature, be highly topical or political, as such publications(25) would prove of fleeting interest. Almanacs, annual publications that contained informationon astronomy and weather patterns arranged according to the days, week, and months ofa given year, provided the perfect steady seller because their information pertained to thelocale in which they would be used Which aspect of colonial printing does the passage mainly discuss?A．Laws governing the printing industry.B．Competition among printersC．Types of publications producedD．Advances in printing technology

单项选择题 地面涂料与内墙涂料的不同，主要是地面涂料应具有（）。

单项选择题 对于基坑宽度大于6m的轻型井点布置宜采用（）。