有序变量也称连续型变量，变量值可取连续不断的实数。
题型：判断题
问题：
有序变量也称连续型变量，变量值可取连续不断的实数。
题型：判断题
Ball Management
Players should always keep a tennis ball in their hand or pocket during a match. Even the most patient tennis players despise waiting for their opponent to find a ball to serve(发球).
Behavior & Attitude
Even if you’re playing badly, you should not shout or look depressed in a friendly match. Undoubtedly, your attitude affects how you play, so try to have fun and stay positive.
Pace
Do not deliberately slow the game down. Play at the pace of the server and look ready. Servers also should not rush to start each point. You should re-do the point if you serve the ball before the receiver is ready. The receiver is out of luck, however, if he claims he was not ready after making an attempt at returning the serve.
For Spetators(观众)
Cheering
While it is seen as proper etiquette(礼仪）to remain silent during the live play, loud and spirited cheers are welcome after a hard-earned point. The players appreciate the recognition for their efforts and are encouraged to continue playing at a high level when the crowd is actively involved.
Leaving and returning to your seat
During live play it’s expected that all spectators will remain seated until the next break between games. Movements in the stands(看台) can serve as a distraction(分心的事物) to the players and can also block the view of other audience.
Photography
The issue of camera shutter(快门) noise has earned a lot of attention in golf, but luckily for tennis fans it’s much less of a concern on the court. While the noise produced by the camera is not seen as a major issue, flash photography should be avoided during live play.
小题1:During warm-ups, tennis player ______________.
A．ought to hit a full pace
B．can place their shots anywhere
C．should not practice competitively
D．had better run around the whole court小题2:According to the text, during tennis matches, _____________________.
A．players can slow the game down when tired
B．players don’t have to keep a ball in their hand
C．the receiver shouldn’t return the serve if not ready
D．loud cheers are not allowed even after hard-earned points小题3:It can be inferred from the last paragraph that ____________________.
A．flash photography is acceptable on the golf court
B．tennis fans can use flash photography during matches
C．the noise from cameras is not permitted in tennis matches
D．tennis matches require a less degree of quiet than golf ones小题4:What’s the text mainly about?
A．Some tips for tennis players to win a match.
B．What to do while watching tennis matches.
C．How to behave properly in tennis matches.
D．Rules tennis players must obey in matches.
）和物质Y（
）的化学反应如下图所示：