I strongly agree with I strongly agree with MCCCHUK
The correct subordinating conjunction is "yet" and the sentence is completed as follows:
Mandy practiced karate every day, yet she failed to beat her final opponent.
The word "yet" is a subordinating conjunction that means "nevertheless" or "however", it is associated with negative statements in order to mention that an event did not take place.
In this sentence, it explains that even though Mandy had practiced she did not beat her opponent.
Maybe passive?
I’m assuming it’d be passive.
An idea that is not actually stated in the text, but is kind of referred to, would be an alliteration I believe.
If I was writing a thesis for that topic I would choose B, because it is asking a question. Choice A is also asking a question but the topic is different because you are asking about the general public. Best of luck to you!