The cries of the kittens echoed throughout the shelter even though fewer cats than usual were there.
a. echod
b. ekoed
c. eckoed
d. correct as is

Correct as is. 
"Echoed" is the correct word to use here. 
"Ecod" is not a word.
"Ekoed" is not a word.
"Eckoed" is also not a word. 

The details that best show evidence of tribal traditions are, "never in the history of his people had a man married a woman who spoke a different tongue” and "it has never been heard," was the verdict of an old man speaking a few weeks later.