He visited his parents last weekend改为否定句和一般疑问

楼主的这个句子有误，正确表达应该是：This is my friend.

• 否定句：This isn't my friend.

  含be动词的否定句是在be动词的具体形式后加not。又如：

  I am a student.---I am not a student.

  They are at school. ---They aren't at school.

• 一般疑问句：Is this your friend?

  1) 含be动词的一般疑问句是将be动词的具体形式提前到句首。又如：

  Tom is in red.---Is Tom in red?

  His parents are teachers.---Are his parents teachers?

  2) 陈述句中的第一人称的代词，在疑问句中要改成对应的第二人称的代词。又如：

  I am a student.---Are you a student?

  It is mine.---Is it yours?

否定：
He didn't visit his parents last weekend.
一般疑问句：
Did he visit his parents last weekend？