creating a string in a buffer

I am having problems again.

I have a char array buffer that is 50 elements long. It is initialized so all elems are Null \0. I also have a 2D array of strings that are defined. I have to randomly select one column in each row in the matrix to determine which string to put into the buffer. it's like this:

static char *source [ROWS][COLS] =
{ {"A", "The", "one"},
{" red", " polka-dot", " yellow"},
.
.
.
}
so it randomly generates a sentence. Should I use strcpy or strcat to get these strings into buffer? especially when I don't know what each one's size is? How??

First use strcpy on the first string, then use strcat on the rest.