The Spanish letter C can be pronounced in two different ways.
1. When the C precedes an E or an I, it is a soft C and is pronounced like a TH (in Spain)* or an S (in Latin America).
2. When the C precedes an A, O, U, or a consonant it is a hard C and is pronounced like a K.
*This is what you will hear in the sound files.
Please note that this explanation is only a guideline for the Spanish that I know, which is Castilian Spanish. There are many regional variations in Spanish pronunciation.