ei or ie?

Quite a few students have trouble spelling the word "receive" right. Based on my observation, I conclude that when it comes to "ei" or "ie" pronounced as /i/, the letter before the combination is a decisive factor. If the letter is "c" or "s," then the spelling should be "ei." Otherwise, it is "ie." To put it more simply, "i" has a straight line, so "ie" comes after a letter with a straight line. Here are some examples: receive, seize, yield, thief, brief, etc. Interesting, isn't it?