[单项选择]天津保护器组装完后，下轴头应在法兰平面内（）mm。
A. 30±2
B. 30±0.8
C. 30±0.5
D. 55±2

差异性市场策略是指企业在对整体市场细分的基础上，针对每个细分市场的需求特点，设计和生产不同的产品，制定并实施不同的市场营销组合策略（各种营销手段的综合运用），试图以差异性的产品满足差异性的市场需求。
根据上述定义，下列属于差异性市场策略的是（）。

Public response to technology often varies in peculiar ways. While biotechnology, for example, gives rise to organized opposition, information technology, which is actually no less invasive (侵害的) ,no more harmless, is welcomed or, at the least, accepted with comparatively little debate.
Information technologies from computers and communications have obviously had an overwhelming social impact and their benefits hardly need explanations, but they have also disturbed privacy and threatened civil liberties, computerized data banks empower bureaucratic authorities by providing easy access to personal information-about credit ratings, social performance, housing and medical histories. They will allow access to genetic figures, providing information about our tendencies to employers, insurers, product advertisers, banks and other institutions that exercise control over our lives. Computerization allows the severe extension of advertising through telemarketing requests t
A. quite evident
B. hard to explain
C. being overcome social opposition
D. to benefit few people