Many students ______ chances to show themselves in class because the class size is too big.
如图所示,一根弹性杆的一端固定在倾角为30°的斜面上,杆的另一端固定一个重力为2N的小球,小球处于静止状态,则弹性杆对小球的弹力( )
棉农在种植棉花植株时常常进行“掐尖”,其原因是( )