Answer: A
Step-by-step explanation:
Waverly's mother is upset that she often loses chess pieces to her opponent, which is made clear when she says "Next time win more, lose less." Because of that and the other comments, we know that it's not B or C, because she never said anything that insinuates that she wants Waverly to lose or stop playing. Although her mother is happy when Waverly wins again, she never says anything about wanting her to be successful, so it's not D.
Basically, A is the correct answer because Waverly would lose less pieces if she blocked her opponent, and her mother wants her to lose less chess pieces.