Question #: 7: They wanted to join an union, but their bosses were against it.
User's answer: True
Correct answer: False
Additional Notes: We use a before a consonant sound and an before a vowel sound. Here, the word starts with a consonant sound.

I did this English test 'Articles - A & An' and above is one the questions I did wrongly.I don't understand what is a consonant sound as I know vowels are,(a,e,i,o,u).

Could anyone please help me with it?