如果H1H2分别表示在拉萨和上海地区空中打开降落伞的最低安全高度，可以判断（） ["H1>H2","H1=H2","H1<H2","H1H2之间关系无法确定"]
要求在图上能表示出0.5m的精度，则所用的测图比例尺至少为（）。 ["1\/500","1\/5000","1\/50000","1\/10000"]
How should you signal the crane operator to raise the boom?（）. ["Extend arm with the thumb pointing up and flex the fingers in and out","Place both fists in front of the body with the thumbs pointing upward","With forearm vertical and forefinger pointing up,move hand in small horizond circles","Extend arm with the fingers closed and thumb upward"]
配网状态检修的基本原则有：坚持安全第一、坚持“标准先行、（）。 ["坚持应修必修","坚持过程管控","坚持持续完善","坚持统筹兼顾、突出重点"]
How should you signal the crane operator to stop in an emergency?（）. ["Extend arm with the palm down and and hold this position rigidly","Place clasped hands in frontof your body","extend arm and move hand rapidly right and left with the plam outward","Place both fists in front of the body with the thumbs pointing outward"]
简述社会营销观念产生的背景。
