Answer:
Hi!
The answer to this would be option A, Stereos.
Step-by-step explanation:
Echo and mosquito are words that require their ending to be changed to "es" in order to be converted from singular to plural. So the plural of echo and mosquito would be echoes and mosquitoes.
In the case of shampoo, the rule is different and the word needs just a letter "s" at the end to become plural. Therefore, the plural of shampoo would be shampoos (speaking in reference to various types or a collection of shampoos).
Just like "shampoo", "stereo" also needs a letter s at the end of the word to become plural. Therefore, the word stereos is correct.