p():text&be followed by a blank line
  p(style="font-family: 'times';font-sil6pt")
  strong():make bold text without "blank line"
  em():create italicized (斜体）text without "blank line"
  code(): similar to computer code
  div(): creates segments of text
  span: same to 'div',but it works with groups of words that appear insde paragraph