It was stated in the instruction with the enlistment letter

"But the enlistment letter stated clearly that we were to wear the given clothes when reporting."

"So you want to enlist into WAC?" The sergeant screamed again.

"No Madame."

"Don't call me a Madame. Call me Sergeant. That applies to each and everyone of you. I am Sergeant Rin, I will be your mother, father, best friend, worst enemy for the rest of Basic Military Training. That includes the sissy here. So answer me now, were you given a bra?"

"Yes Sergeant." You shouted.

"And where is it?"

"It's in my bag."

"Why aren't you wearing the bra since the enlistment letter said so?" Sergeant Rin shouted again.

You were dumbfounded. You could say that you didn't know how to wear or you could say that you refused to wear because you were a guy.