How do we know when to use a c in the words that have k sound beginning?

It's not always easy to tell when to use a "c" for a "k" sound at the beginning of a word, but here are some general guidelines:

1. The "c" before "e", "i", and "y" usually makes a "s" sound.

* Examples: cent, city, cycle

2. The "c" before other letters usually makes a "k" sound.

* Examples: cat, car, cold

3. There are some exceptions to these rules.

* Words of Greek origin often use "c" for a "k" sound.

* Examples: cyclone, cephalic, chronic

* Some words have "c" for "k" even before "e", "i", and "y" for historical reasons.

* Examples: cemetery, circuit, cider

4. When in doubt, check a dictionary.

Here are some additional points to remember:

* The "ch" combination often makes a "k" sound.

* Examples: character, chorus, chronic

* The "ck" combination always makes a "k" sound.

* Examples: clock, tack, quick

Ultimately, the best way to learn these spelling rules is through practice and exposure to the English language. Reading widely and paying attention to how words are spelled can help you develop your understanding of these patterns.