四级阅读理解之二Passsage 1As the merchant class expanded in the eighteenth century North American Colonies, the silversmith and the coppersmith business ro to rve it. Only a few silversmiths were availa
ecent advancements in pla-nar optics technology , specifi-cally in the area of optical splitters, switches, modula-tors, and wavelength-divi-sion multiplexers, are driving demand for immediate increas