题目

With the advent（出现） of fast food chains from the West such as McDonald's, Kentucky Fried Chicken and Pizza Hut, the Chinese are being introduced to a diet that markedly（明显地） increases the death rate from certain diseases in any population. The main killers in North America, the degenerative diseases（变性疾病）such as heart attack and stroke as well as colon（结肠） cancer, will become a way of death in this country if the Chinese do not act quickly and compete with these health destroying food chains.Scientific studies from all over the world show that a di常见电路连接方式一般有______和______两种，生活中小彩灯的电路就属于______电路，而家庭电路中的各个用电器之间是______的，用电器和控制它们的开关是______的；两种电路中用电器工作特点的主要区别是能不能______（选填“同时”或“单独”）工作，若所有用电器可以同时工作，也可以同时不工作，则电路______（选填“一定”或“不一定”）是并联的．