"Quando o espetáculo começa?"

Translation: When does the show start?

[Lingodingle]

Does começa take the mark under the c but comecei does not? One exercise wanted it, the other didn't want it.

[r_i_l_e_y]

If the next letter is an "e" or "i" then "c" is used, and not "ç"

[Paulenrique]

That happens to keep the same sound. The letter C followed by O, U or A sounds like K. To keep the same C sound /S, SS/ you use Ç. So we say começar and começo, but comece, for instance.