下列哪些选项不是腾讯云关系型数据库产品的应用场景？
A. 型线上游戏，用户数据对于游戏非常重要，发生故障时需减少损失。
B. 互联网/APP的应用场景，用户访问量大，访问时间比较集中，用户读取请求远大于写入请求，数据库压力大。
C. 电子商务网站某些数据访问量非常高，数据库相应存在延迟。
D. 电商、金融、 O2O、社交应用、零售、 SaaS服务提供商，普遍存在用户基数大（百万级或以上）、营销活动频繁、核心交易系统数据库响应日益变慢的问题，制约业务发展。
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The temperature of cold packs is lowered when crystals of ammoniumnitrate are dissolved in water. Which of the following is true of thisreaction?
A. ΔH = 0, since cold packs are sealed
B. ΔH > 0, process is exothermic
C. ΔH < 0, process is exothermic
D. ΔH > 0, process is endothermic
E. ΔH < 0, process is endothermic
Given: 2Al + Fe2O3 → 2Fe + Al2O3 ΔrH = -850 kJWhat is the ΔrH for 4Fe + 2Al2O3 → 4 Al + 2Fe2O3?
A. +850 kJ
B. +1700 kJ
C. -1700 kJ
D. +425 kJ
Reaction rates are affected by concentration, collision geometry,temperature and the presence of a catalyst. Which one of the followingstatements is FALSE?
A. Larger concentrations of reacting particles increase the number ofcollisions.
B. Molecules that do not collide in the correct orientation lower thereaction rate.
C. A catalyst increases the speeds of the reacting particles.
D. Raising the temperature increases the effectiveness of collisions
Which statement explains why the rate of some chemical reactions isincreased when the surface area of the reactant is increased?
A. This change alters the electrical conductivity of the reactant particles.
B. This change increases the density of the reactant particles.
C. This change exposes more reactant particles to a possible collision.
D. This change increases the concentration of the reactant.
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