The letter "c" can have different sounds depending on the letter that follows it.
Here are some common patterns:
* "c" followed by "a", "o", or "u" often makes the "k" sound: cat, coat, cup
* "c" followed by "e", "i", or "y" often makes the "s" sound: cell, city, cycle
* "c" followed by "h" often makes the "ch" sound: chair, chef, choose
Of course, there are exceptions to these rules. For example, "ce" at the end of a word can make the "s" sound: dance, fence, prince.
The best way to learn how to spell words is to practice! Read widely, use a dictionary or spell checker, and remember the common spelling patterns.