I'm a high school student. i used to get  A marks in my all examinations but unfortunaltely I can't get A marks recently and the reason refres to my carelessness. what would you recommend me to improve and being accurate during an exam?
Well study and review right before the test. It sounds to me that you need some improvement in your study skills! Try writing the info down or typing it out, it might help!
TIMING is the key. volleys requires u to be consistant, dont try to add power to ur shots, that'll take away ur accuracy. see where u wanne bounce the ball on the oppsite side. better net speed comes with accuracy as well. try to hit the ball away from ur opponent, make them run a little so u can come up to the net; ur accuracy goes down when u are hitting the ball while running. and for better footwork try to run the lines on the tennis court during practice or prior to the game, that will give u speed and mobility.