关于英文Caesar一次的发音Caesar (凯撒)第一个字母C发音是像 S 还是 为什么外国人读做S音呢?那不就成"西

Why " Caesar " phonetically translated to "Kai Sart" !
i guess it's those days while English language wasn't popular over China and Asian territories.So people just try their best to create closer pronunciation to it.
1.1 Look at Sherlock Holmes,the word "Holmes" "translated" to Fook Yee Mor See" then you'll know how clumsy Chinese people were in those days while learning English language (actually even now!) !
2.On the other hand,in Italian (Roman Empire) language,letter "C" is sometimes pronounced as "chi" like "Gucci",and sometimes,though not commonly,pronounced as "K".So,that's why it becomes "Kaesar".Then,the pronunciation is close to "Oi Sart"!
演讲时一定要读/s/音

那要看台下听的是什么人群了 如果那些人都读“K”（学生、老师）那你读"K" 但是如果下面都是老外拉 华侨啦什么的 那你还是读“S”吧 毕竟符合别人的口味最重要

你做英文演讲的时候就是要发s 的音。即：si;ze 反正是要按音标来的。
至于翻译，其实随意性很大，尤其是人名，大家觉得这么叫顺口，所以都这么叫，逐渐就成为约定俗成的了。

当然是s了

当然是/s/音了，至于叫凯撒，那是咱们要这样叫

Caesar
[si:zE]
n.
凯撒(古罗马的将军,政治家,历史家,公元前100-44)