Youth sport has the potential to accomplish three important objectives in children’s development. First, sport programs can provide youth with opportunities to be physically active, which can lead to improved physical health. Second, youth sport programs have long been considered important to youth’s psychosocial development, providing opportunities to learn important life skills such as cooperation, discipline, leadership, and self-control. Third, youth sport programs are critical for the learning of motor skills; these motor skills serve as a foundation for future national sport stars and recreational adult sport participants. When coachers develop activities for youth practices and when sport organizations design youth-sport programs, they must consider the implication of deliberate play and deliberate practice.
    Research from Telama (2006) states that regular participation in deliberate play or deliberate practice activities during childhood and youth (ages nine to eighteen) increases the likelihood of participation in sports during adulthood by six times for both males and females. C?té (2002) defines deliberate play activities in sport as those designed to maximize enjoyment. These activities are regulated by flexible rules adapted from standardized sport rules and are set up by the children or by an involved adult. Children typically change rules to find a point where their game is similar to the actual sport but still allows for play at their level. For example, children may change soccer and basketball rules to suit their needs and environment (e.g. in the street. on a playing field or in someone’s backyard). When involved in deliberate play activities, children are less concerned with the outcome of their outcome of their behavior. (whether they win or lose) than with the behavior. (having fun).
    On the other hand, Ericsson (1993) suggests that the most effective learning occurs through involvement in highly structured activities defined as deliberate practice. Deliberate practice activities require effort, produce no immediate rewards, and are motivated by the goal of improving performance rather than the goal of enjoyment. When individuals are involved in deliberate play, they experiment with different combinations of behaviors, but not necessarily in the most effective way to improve performance. In contrast, when individuals are involved in deliberate practice, they exhibit behavior. focused on improving performance by the most effective means available. For example, the backhand skills in tennis could be learned and improved over time by playing matches or by creating fun practice situations. However, players could more effectively improve their backhand performance by practicing drills that might be considered less enjoyable. Although drills are used in most effective means available practice might not be the most enjoyable, they might be the most relevant to improving performance.

洒水车的水箱是一个横放的椭圆柱体，尺寸如图，当水箱装满水时，计算水箱的一个端面所受的总压力.

甲、乙、丙演示图，显示了森林、草地所具有的哪些作用（    ）
①防风固沙；     ②防止水土流失；    ③涵养水源；     ④维护生物多样性；

洒水车的水箱是一个横放的椭圆柱体，尺寸如图，当水箱装满水时，计算水箱的一个端面所受的总压力.

洒水车的水箱是一个横放的椭圆柱体，尺寸如图，当水箱装满水时，计算水箱的一个端面所受的总压力.

洒水车的水箱是一个横放的椭圆柱体，尺寸如图，当水箱装满水时，计算水箱的一个端面所受的总压力.