题干

雷雨天闪电时空气中有臭氧(O3)生成。下列说法中正确的是

A:相同质量的O2和O3原子个数比为2:3

B:O2和O3化学性质完全相同

C:在相同温度与压强下,等体积的O2和O3含有相同的分子数

D:O2和O3的相互转化是物理变化

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答案(点此获取答案解析)

C

同类题3

根据短文内容, 从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    NBA basketball players devote much of their lives to preparing for games. This preparation, which includes studying game films, practicing skills and treating injuries, is essential because of the pressure-packed nature of their profession.

    ____ Generally, on the day of a game, players get together in the morning for an hour shooting and also to review films of the opponent of that night. ____ Players receive treatments for injuries, put on their uniforms, discuss strategies(策略) with coaches and warm up during the remaining time before the game gets underway. As thousands of people cheer them on, a team's best players will play 40 or more minutes during the game. After the game, some players stick around to lift weights before showering and heading home.

    ____ They must leave their families at home, spend hours on planes traveling around the country and try to stay rested while sleeping at a different hotel every night.

    The NBA's 82-game regular season is tiring. ____ So many players focus on recuperating(恢复) for at least part of the off-season. Other players, may work on recovering from surgery to correct injuries.

    Weeks before the training camp, NBA basketball players start getting back in shape for the upcoming season. ____ Younger players often take part in developmental leagues during the summer months to increase their chances of getting onto an NBA team.

A.Trips can be difficult for NBA basketball players.

B.The league was founded in New York City on June 6, 1946.

C.It can even make the best-conditioned athletes tired.

D.It consists of 30 teams, 29 in the US and 1 in Canada.

E.The preparation may involve practicing basketball skills and lifting weights.

F.Following lunch, many players take a nap and eat a pre-game meal before arriving at the field.

G.An NBA basketball player's typical workday routine varies based on his team's schedule of games.