Answer: A.
Explaniton:
Although you might not want to speak publicly about your project, if you do good enough you'll be rewarded! We aren't rewarded when actually speaking with people, but its good to know you did well because that'll make you more confident to talk to others just the same way.
D. by describing the different sports.
because he is explaining the different sports to let people know what they are like and the benefits of it.
Fifty cents is a plural noun since it is talking about more than one cent. In the example, you would say, "fifty cents <em>is </em>how much I owe you".
