如图为探究灯泡两端电压与电流关系的电路图，下列说法错误的是（　　）

【查阅资料】普通蜡烛由石蜡和蜡烛芯制成,而吹不灭的蜡烛是在蜡烛芯上包裹一层打火石的粉末,打火石是由某种金属掺入少量稀土元素制成的合金,它的着火点只有150℃，当蜡烛吹灭后,未冷却的金属继续燃烧,从而使蜡烛复燃。吹不灭的蜡烛芯外的金属可能是镁、铝、铁或铜中的一种,为确定该金属的成分,他们进行了下面的探究。(不考虑打火石中稀土元素对探究金属性质的影响)

【提出问题】“吹不灭蜡烛”打火石中含有哪种金属?

【做出猜想】

猜想一:该金属是Cu            猜想二：该金属是Fe

猜想三:该金属是Mg            猜想四:该金属是Al

【实验探究】同学们根据所学的化学知识设计并进行如下实验确定该金属的成分.

质量为m的物体静止在倾角为θ的斜面上，当斜面沿水平方向向右匀速移动了距离s时，如图所示，物体m相对斜面静止，则下列说法中正确的是（   ）

以恰当的方式表达男女同学的友情，应该做到（    ）

    Arthur Robert Ashe Jr. was the first African-American player to take part in the international sport of tennis at the highest level of the game. He was born on July 10, 1943.
    When Arthur was 6, his mother died. Arthur, with his father and his brother, lived near a large park in Richmond, Virginia. His father was the manager of the park. He took care of the park and made sure everything was right. 
    Arthur was allowed to play in the park when he was seven years old. He was quite energetic. A swimming pool, tennis courts, and baseball diamonds (棒球场) were in the park. Arthur spent a lot of time playing there. He did well in sports, but he had never tried to play tennis.
He often watched the tennis players. Sometimes there were tennis lessons, and Arthur would watch even more carefully. The young man teaching the lessons noticed Arthur. His name was Ronald Charity.
    Mr. Charity asked Arthur if he wanted to learn to play tennis. Arthur was excited and agreed. Arthur learned very quickly. Mr. Charity found Arthur would grow up to be a good tennis player. By the time he was ten, Arthur won a tournament (联赛). Many older and bigger players came to the park trying to win the prize, but Arthur beat them. He became known as “the kid who could play tennis”.
Arthur grew up to be one of the first successful African-American tennis players. He played and won all over the world.