①你这位姑娘显得那么谦让、美丽、善良。

②小井周围的树苗已经长成枝叶强壮的大树。

③草地上还有鹿和兔子跑过的事迹。

④清澈的泉水仍旧那样清净地流着。

    People have all turned to sad music to make themselves feel better at some point in their lives, ____why does the music with double or even triple sadness help drag people out of low spirits?

    A new study throws light on what's going on inside people's brains when they match their music to their feelings, and it looks as if sad music can be enjoyable, rather than____(simple) depressing. Music of this sort can arouse positive memories in people's life , thus ____(lift)their mood.

    Psychologist Adrian North from Curtin University in Australia says there____(existence) two groups of possible explanations for why people enjoy listening to sad music like this---one from social psychology, and the other from cognitive neuroscience(神经学).

    ____terms of social psychology, one idea about this is that people will feel____(good) about themselves if they focus on someone who's doing even worse. Everything's going to be okay, because this person is having ____even worse day than they are.

    Another idea from social psychology is that people like to listen to the very music____shows their present life circumstances, because this kind of music makes them feel they are understood. With their emotions____(share), they definitely get a certain amount of comfort.

    So, the____(conclude) again—sad music does cheer people up, and it works far better than happy music, in most cases.

用加减法解方程组$\left\{\begin{array}{c}x+y=5\\ x-y=-1\end{array}\right.$C中，消x用____法，消y用____法（　　）

如果m是一个有理数，那么－m是（   ）。