第17题: [单项选择]含有组胺和过敏性反应物质的是() A. 中性粒细胞 B. 嗜酸性粒细胞 C. 嗜碱性粒细胞 D. 血小板 E. 红细胞 参考答案:C 答案解析:嗜碱性粒细胞颗粒内含有组胺和过敏性慢反应物质,可使毛细血管壁通透性增加,局部充血水肿,并可使支气管平滑肌收缩,从而引起荨麻疹、哮喘等变态反应。
第20题: [单项选择]If the radio signal ground wave extends out for less distance than the minimum skywave distance,there is an area in which no signal is received.This is called the(). A. Skip zone B. Blackout zone C. Diffraction zone D. Shadow zone 参考答案:A