____，壮士一去兮不复还。（《荆轲刺秦王》）

   If babies are given more love and feelings by their mothers, they will deal better with stress and anxiety when they grow up , research has shown.
   The study of eight-month-old children shows even the very earliest life experiences can influence our happiness.
   Lots of mother love makes children form a safe bond with their mothers , so they are able to feel safe in relationships when they grow up ,and they will have better social skills and deal with life's difficulties．
   The researchers,  led by Dr．Joanna Maselko of Duke University in North Carolina,  studied the relationships of 482 eight—month - old  babies with their mothers during daily development.
   They studied how well the mother had dealt with her child's developmental text and how she had responded child's performance．Mental health was then assessed when the babies had grown up – at the average of 34.
   The more feelings and attention a mother gave to her child, the better her child would be. This kind of child had the lowest levels of anxiety, hostility and general difficulties.

如图所示，（a）图中⊗表示导体中电流方向垂直纸面指向纸内时，导体在磁场中的受力方向。试根据这一关系，标出（b）图中通电导体的受力方向，（c）图中通电导体中的电流方向以及（d）图中的磁极。