Learn French: C'est ma cinquième question. - This is my fifth question.

We use C'est because it is followed by a modified noun (ma cinquième question). If you were just using an adjective, you would use Elle est (for example, Elle est difficile). But whenever you have a determiner like ma, une, or la before a noun, you must use C'est.

Why is there an extra u in cinquième when the number five is just cinq?

In French, the letter q usually needs to be followed by a u before another vowel to keep the hard K sound. When adding the -ième ending to cinq to make it an ordinal number (fifth), we must add that u to get cinquième.

Does the ordinal number cinquième change depending on the gender of the noun?

No, unlike the possessive ma, the word cinquième does not change for masculine or feminine nouns. It works for both. However, it would take an s at the end if the noun were plural.

Since question is spelled exactly like the English word, do we pronounce the -tion ending the normal French way?