Could you please give me a hand, thank you.
Letter C usually pronounes [s] before e/i/y, for example, city, but I found sometimes it is pronounced "sh", (appreciate, excruciate). Is there a rule about it?
thanks in advance
A person in the UK would say: "appresi-ate" (to use your lettering reference)
A person in New York would say: "appreshe-ate"
It is not unlike the word "privacy" which is quite differently pronounced in America and the UK.
Some people will use more than one variation depending on with whom they are speaking.
Just go with the flow wherever you happen to be located.