Particle + Verb to Speak

This is simple, but I keep seeing two ways of saying, "Do you speak English".
Often, I see it as: Eigo o hanasemasu ka. But, the present tense of the verb "to speak" is はなします、not はなせます. So, is it hanaSEmasu ka, or hanaSHImasu ka?

Also, I see it with two different particles, sometimes を, and sometimes が . I think "o" is the right one... correct?

はなせます is the potential form.
Japanese verb conjugation - Wikipedia, the free encyclopedia

が indicates the object of potential verbs, as in the explanation in the wiki page I linked above. を also can be used, though.